Disclosure: This site may receive compensation when you click on some links and make purchases.

$3,200 Diesel: 1980 Pontiac Bonneville Brougham


This is a rare one: a 1980 Pontiac Bonneville Brougham and it’s a two-door coupe. And, it’s a diesel! It’s listed on eBay in Bay Shore, New York with a Buy It Now price of $3,200. This one would get a lot of looks at almost any car show.


I think that this is a beautiful body style, especially in a two-door coupe configuration as seen here. The seller says that it was dealer-Ziebarted so there’s “NO RUST” at all! Not even on the bottoms of the doors! This is a sixth-generation Bonneville and in 1980 they received a facelift with a bit more aerodynamics and weight reduction. It looks like the rear wheel skirts/spats are a bit darker; maybe they weren’t used and the rest of the paint faded a bit? And, then there’s that odd little square piece on each side in the rear by the bumper ends that’s also a little darker than the body paint is, does anyone know what those are for, or from? They aren’t shown on the 1979 Bonneville. They’re also in front. I’m guessing that it’s a plastic/vinyl piece from a previous wrap-around bumper?

This car looks great, in my opinion. I think that this is one of the most elegant bodies for Bonneville with the upright rear glass and that classic, padded landau roof.


The interior is a bit of a 36-year old time capsule; a study in velour. Everything looks like it’s in fantastic condition, from the door panels to the rear seat to the working 8-track player.


Here’s the really rare part, Oldsmobile’s 350, 5.7L diesel which was a $790 option in 1980! That equates to around $2,300 today. The 105 hp offered in the diesel doesn’t seem like a lot for a two-ton car, and it isn’t. But, in those days it was all about MPG and this diesel got around 18 mpg compared to around 14 for a similarly-sized gas engine, when it was working properly, which was why they were only offered for two years. And, before it it comes up, and it will, it’ll take a long time to pay off that $790 diesel up-charge when you’re only getting another 4 mpg. This car looks super nice to me. It would sure be interesting to park it at a car show and field questions about the diesel, there aren’t many diesels still out there. Do you remember this era of GM diesels in full-sized cars? Do you think that the working diesel option helps or hurts the desirability, or the value, of this car?


  1. mark

    Ah yes the GM 5.7 Liter diesel. Actually a 350 Chevy small block that GM converted to and then called it a diesel. Absolutely gutless and smoked like no tomorrow when under load. You could get this same motor in an Oldsmobile Delta 88 and GMC/Chevy pick ups. The used car lots were full of these things within 2 years of them being sold. If this thing has low mileage it is that way because they were absolutely miserable to drive. A relative had an Olds version of this. These things made 4 cylinder Vegas and Pintos seem like speed demons.

    Like 4
    • St. Ramone de V8

      I thought that Diesel was an Olds based engine? I think that by offering it in the luxury cars they were going after the Euro cars. My brother had an Eldorado with one, and when it died an early death, it was converted to propane with an Olds 350 donor. That Caddy never did run on gas!

      Like 3
      • Brian

        GM offered that engine in virtually all full and mid-sized cars. GM did make an attempt to upgrade the 5.7 liter for diesel but the short comings were many. I recall there is an entire book on this disaster. Everyone was going nuts over a few mpg and the result was some of the worst driving cars in history. My first job out of college included a company car. A 1978 Malibu with a 200 ci v-6. Two options, AM radio and A/C. It was slow to the point of dangerous.

        Like 1
    • geomechs geomechs Member

      Hi mark. Actually it was an Oldsmobile engine. And it was NOT a reworked gas motor. Very few parts interchanged between the gas and the diesel if the truth be known.

      Like 8
      • DrinkinGasoline


        Like 1
      • Arve

        The basic engine construction is the same as the gas olds, but that should not be an issue. Many other diesel engines are also derived from gas engines and are no less durable for that matter. Examples are Nissan LD engines, VW and Peugeot diesels.

        Like 2
    • DrinkinGasoline

      Ah No….. It was not a GM platform diesel engine. It was not a Chevrolet 350 engine. It was an Oldsmobile Motor Division based diesel project engine. Your relative had the Oldsmobile Diesel engine. As far as Vegas and Pintos go….I think that’s an extenuated reach . Apples vs. Oranges. If what you state is true, why didn’t all of the GMC and Chevy pick-ups of the same years experience the same “smoke like no tomorrow” syndrome ?? Why ? Because they were not the same engine…that’s why. It was a OMD engine.

      Like 3
    • Jay Calk

      I think you got off on your diesel description. Yes it was a 350 but the crank shaft and heads were heavy duty. Some one gave me a diesel motor and I tore it down changed the can and added a distributer and four barrel carb and that thing had some torque. I was told the bottom end was from the 455. As a diesel motor they were terrible but got over 20 mpg in 5000 lbs car.

      Like 1
      • Jim

        Guilty as charged, I guess I had a nerdgasm! I’ve spent a bunch of time in the hospital and haven’t talked shop much.

        Like 0
    • Bruce

      Actually they were not that bad to drive as they were heavy. True, they were no speed demon but once up to speed with some diesel torque, they were fine. I drove my 81 Pontiac Bonneville for over 200k after a blown engine at 100k and two transmission over-hauls. The second Target GM Diesel blew for the second time at around 100k. I donated it to the Rawhide Boy’s Ranch in Green Bay, WI.

      Like 0
    • Ed

      The Olds 5.7L Diesel, the LF9 engine,
      In 1978-1980(beginning) had no water separators nor warning lights, main bearing caps screws where too short, weak head bolts (same as gas engine bolt pattern)
      The initial problems were 2 fold, drivers that didn’t understand not to use “dry gas” in a diesel as the the o-ring in the injection pump would disintegrate cause a rebuild on the pump, main bearing bolts would tear out, gas oil used in a Diesel engine ( SF/CC or SF/CD required), wrong weights of oil, or if a head gasket leak occurred, they would only replace the broken bolt reused the others(which typically has stressed fractures from A. Being re-torqued or from the 22.5:1 compression ratio. Head gaskets with fire rings that weren’t large enough added to the problem. They didn’t have roller can lifters so the oil changes, every 3000 miles and correct oil were imperative, now add that up to mechanics whom were completely unfamiliar with a Diesel engine and you have a problem….
      1981 saw deep met main bearing bolts(issue was solved), water in fuel warning lights, hydraulic roller cam lifters, stronger TTY head bolts, improved head gaskets fixed many issues. However drivers and mechanics still are playing a roll but are becoming better educated.
      The typical LF9 motor would see 21 mpg city and 32 mpg highway vs the gas 350 getting 14 mpg city and 21 mpg highway.
      The one fix was to stud the engine with ARP head bolts and a Victor Reins head gasket, I still have 3 1972 Buick Diesel Rivieras with 150,000+ miles and original engines with those 2 upgrades. I change oil every 3000 miles and use Kendall Super D3 30w oil, good diesel fuel, Stanadyne diesel fuel conditioner and am still getting 30mpg on the highway.
      And to be clear yes it has the same bore and stroke as it’s gas counterpart, however it has 5 main bearing caps, a 3” crankshaft VS 2.5” crankshaft, thicker block walls webbing, completely different heads etc. it WAS NOT a gas conversion it is a TRUE Diesel!!!

      Like 1
  2. Slim Chance

    The engine is junk. Another GM bone-head maneuver almost as bad as the Cadillac Cimmaron…. I mean Chevy Cavalier.

    Like 0
  3. Rock On Member

    Would really help to put a Duramax diesel in this car. More power and better fuel economy.

    Like 0
    • geomechs geomechs Member

      Installing a Duramax wouldn`t be all that bad an idea if only you could find the room.

      Like 1
    • Andrew

      My friend installed a Duramax in a ’63 Caddy this year. Was a very tight fit and a HUGE undertaking, but it works very well. You can probably find it if you search #cadimax. Cool build, but not for the rookie.

      Like 0
  4. geomechs geomechs Member

    Nice car! I have no doubt that a lot of people are going to shy away from this one because of the diesel motor. Myself, I tend to sway the other way because I worked on lots of them and know what makes them tick. Personally I’m more partial to a similar vintage Cadillac Eldorado with a diesel motor. I looked after one for a customer for a few years back then and would love to find one just like it.

    We sold and serviced a pile of diesels between ’78 and ’84. Mostly pickups but lots of cars as well. The 350 diesel had a questionable reputation but I have to say that it was about as misunderstood as a motor could get. It wasn’t a bad motor overall. People flocked after them because they were rumored to be super economical. Unfortunately the typical stop-n-go driving of the average motorist caused the motors to sludge up and all sorts of problems showed up as a result. One thing I couldn’t understand was that the average service department was scared to death of the 350D. If one came in for whatever reason they automatically switched out the injection pump and/or injectors. I could never figure out that if a gas engine popped back through the intake you looked for the cause of the exhaust valve not opening; if it was a diesel you replaced the injection system. Whenever we encountered a major engine failure there was usually evidence to show that it was pushed way beyond its limits. I heard people complain of camshaft failures. Back then we had a lot more gas pots rounding off camshafts. Mostly SBC’s but lots of big blocks, and Olds and Buicks too. I might add that Mercedes had a lot of camshaft failures as well. The API made a lot of changes to the oil specification about that time and I think that might have led to some failures. It seemed odd that the moment they changed the spec to SF the failures stopped.

    Like 3
    • DrinkinGasoline

      The masses looked to them due to the 70’s fuel scare/crisis but were duped.

      Like 0
    • DrinkinGasoline

      The mid 80’s were….the transitional period from divisional engines to GM’s “Platform Service Engines”.

      Like 0
    • Telly Black

      The ’81 diesel Cutlass I bought in ’89 had a Target replacement engine. The original engine failed at 7500 miles due to a broken piston pin…created a “picture window” engine block. Done, of course, but the Target replacement diesel engine was great! The TH200 trans was great as well…

      Like 0
  5. DrinkinGasoline

    Truth be told….the 350 LT1, found in the Caprice Classic and the Buick Roadmaster of the early 90’s would be a much better suited power plant. Another truth told, most were converted to gas within 5 years of sale so this one could be considered a survivor.
    I worked for multiple GM dealers as a parts department manager during this time. A Durascrap would not serve this vehicle well at all as the trans and rear differential would not support it. If you’re into numerous Stanadyne Injection Pump issues (dealers send them off to Stanadyne per factory service guidelines, per TSB’s) then have at it, but to stay simple and have serviceability….LT1. I would certainly do the transplant on this Bonney.

    Like 0
    • Greg

      You talk too much, partsman.

      Like 0
  6. DRV

    Our shop used a 78 Delta 88 diesel for long distance runs. It went to 200k and we used our John Deere diesel shop oils in it.
    We beat the bejeebees out of it.

    Like 1
  7. rmward194 Member

    What a beautiful car! I remember these well. I worked as a porter for a BCOP store during this time. Those velour interiors required lots of vacuuming to get all the lint off. The dealer I worked for ordered EVERY new car with the 231 V-6 or a Diesel. We never ever stocked a V-8.

    The dealership was in a farming community and the farmers were drawn to the cars. I believe this was because they could use diesel fuel from the farm without having to pay the highway fuel tax. Lots of them went bad and it alienated many customers. GM wound up paying to have most of them fixed. The diesel was available in just about every full and mid-size car GM made including Buicks, Chevrolets, Oldsmobiles and Pontiacs. I even owned a 1981 Grand Prix Diesel for a short time.

    GM also made a smaller 265 c.i. (?) diesel as well IIRC. There weren’t many of those made. They put them in the mid-80’s FWD Buicks and Oldsmobiles if I’m not mistaken.

    A couple years ago this same dealership bought back a similar car from the original owner. He always said when he stopped driving he would want to sell it back to the store. He did as he said and the store bought it back and re-sold it.

    Like 0
    • Trickie Dickie Member

      I don’t know the rules on diesel use in your area or state but in California the rules are very strict. Farm diesel with no road tax is dyed a color, like pink or purple, not sure which. If a road use vehicle is caught with dyed diesel there is a HEAVY fine. Farmers here use diesel pick ups a lot but would never use non taxed fuel in their vehicles.

      Like 1
      • daCabbie

        You think a cops gonna stick a dipstick down in this tank to look for off-road diesel? Most newbie-traffic cops don’t even know what color off-road should be… I burn it in my Mercedes all the time… but I don’t pull the car up to the pump… I bring jerry cans home… but around here its only 10 cents a gallon cheaper.

        Now if you want to save some real money… get ahold of gray-market bio-diesel… NOT WVO! bio-diesel is different…. WVO (waste vegetable oil) requires a conversion …. bio-diesel requires NO conversion.

        Untaxed bio-diesel can be died the same color as street diesel but its a dollar a gallon cheaper… good savings if you drive alot.

        This part is titled: How to make America Great Again… and not advised!

        If you have an old oil furnace tank on your property (that doesn’t leak) then you can keep up to 660 gallons stored on a residential property… add a little preservative to keep it through the winter and you could save yourself a few hundred a year.

        Of course, Someone Who Isn’t Me might do this… I always pay ALL my taxes…

        daCabbie is always on call.

        Like 1
  8. Bubba Smith

    That car is begging for an LS. Instant power, reliability and better economy…not to mention the added cool factor. Great looking car, I would love to have it in my garage.

    Like 0

    They were hated more than they deserved to be hated. Kind of like the Corvair. I knew of a few that went well over 100, 000 miles which was a lot then.
    There was a contractor near me that had a high reach crane… (you know what I’m going to say don’t you). He suspended his diesel Cadillac 50 or 60 feet above the ground. When the media called he said he was going to drop it if he couldn’t get satisfaction from GM. If I remember correctly, they gave him a new gas model. He never dropped it.

    Like 0
  10. chris lawrence

    I owned on of these in 89… horrible, horrible car.

    Like 0
    • DrinkinGasoline

      Why was it horrible?….details?

      Like 0
  11. Telly Black

    I bought a 17,000 mile ’81 Cutlass Broham 2’door, back in ’89, with a Target replacement 5.7 diesel. It seems the factory engine failed at around 7500 miles. I drove that car everywhere…for nearly 200,000 miles, always got 30 mpg, and had to “put-it-to-pasture” because the front end needed rebuilding, and living in Michigan, rust was developing…the engine still lives on, in a log skidder!

    Like 3
  12. Puhnto

    It is my recollection that these diesels (1980 in particular) were considered the worst engine ever made, even by GM dealers. Dad had one in his 1980 Cadillac Seville (the low swoopy ones people either loved or hated — dad loved his) which was a nice engine — when it ran. It spent way too much time in the shop. Father-in-law had one in his big 1980 Oldsmobile. He didn’t have as much trouble with his.

    Like 0
    • Mr. TKD

      If I recall correctly, the diesel was standard and a gas engine was optional. I loved that era Cadillac.

      Like 1
    • jimmy

      My grandmothers when they test drove it to the house they were building to show the salesman they walk back to the car and it had dumped the ATF out all over the driveway and they still bought the car. You also had to get a running start to go up the driveway which the diesel Mercedes never had a problem going up the steep driveway like it wasn’t even there.

      Like 0

      You don’t remember the Caddy 8-6-4 then do you….

      Like 1
  13. grant

    Yuck. Attention at the car show? Only from Grandma looking for a ride home.

    Like 0
  14. Wayne Thomas

    Too expensive to be done, but an engine swap with a newer turbo diesel would make for a great sleeper!

    Like 0
  15. Dan h

    Working on a ’82 El Camino with a 5.7 diesel right now as matter of fact. I think these motors are a little over hated. The heads are susceptible to cracking but other than that they aren’t that bad of an engine (imho). Folks would just expect them to be like a gas motor and or push them beyond what they could handle.

    Like 2
    • juan

      You just need to put mor bolts on the heads and problem solved (not random, of course) but in some cases when you do dath crankshaft cracked (sometimes, not always).

      Like 0
  16. David Montanbeau

    Converted many to gas. Just changed the upper end.

    Like 0
  17. Mr. TKD

    Ooooh, fender skirts! All I need is an LS or LT ready to go and I’m set!

    Like 0
  18. Bruce

    Like DrinkinGasoline, I too worked for a Pontiac/ Olds dealer during that time period. I was the body shop manager but spent a lot of time with the guys in the shop. As was mentioned , a lot of farmers bought them as did long distance salesmen. I even bought a 80 Deville with one. The big problem in our area of the country ( a lot of hills..) seemed to be the # 3 main bearing & crankshaft. The crank would break & sail the bearing cap through the block / oil pan. If it was not under warranty it would get a 350 R Olds engine. That was the ONLY direct fit engine replacement and after awhile the salvage yards jacked the price of them because they were selling so many.
    I never had any issues with mine ( I drove it 30,000 miles & sold it with 90,000) and the guy I sold it to drove it until it split the crank with 160,000 miles.
    The long haul salesmen seemed to have the best luck with them. I think those diesels liked that kind of highway driving. RPM’s remained constant, high enough to keep them clean, but not too high. Diesels don’t like to lug down and I think that was their down fall.
    I remember a LOT of pissed off customers at trade in time…They payed big for the option to have it, and deducted BIG when time to trade as the dealer could not give a used one away. Every one that got traded at our dealership got a 350 R stuffed in it & we had an old building out back stuffed with old diesel engines.
    OPEC & the fuel crisis made car company’s do some crazy things in the 70’s & 80’s….

    Like 1
    • homeboymi

      I worked for the foundry and you are correct about the #3 bearing giving. The bearing bulkheads of a regular 350 weren’t beefed up enough in the beginning to handle a diesel.

      Like 0
  19. Bobsmyuncle

    Didn’t one of these make some internet fame a couple years back? Owner had a blog and took it to SXSW?

    Like 0
  20. Mark

    Those diesels were notoriously unreliable. I would want to swap it out for a 350, which I believe most folks that were stuck with them did back then. If you could get the car cheap enough, it appears to be worth the swap but I wouldn’t buy this as an investment. Put the 350 in and you have a nice Sunday driver or tow vehicle.

    Like 0

    the 350d motor was a sophisticated piece of garbage its successor, the 5.7 litre was much improved, but it was still limited as to what it could be made to do the story is long and involved, but you might be interested to read my experience

    i too worked in a dealership as a service writer and i knew that i would have problems with the majority of those cars because of dupe dupes operating them dupe dupes are those people you see going down the road with a cracked windshield and two low tires and only one headlight and the air conditioning blowing their hair straight back because they cannot get the ac blower to blow the hair completely off their head i am sorry, but i had to get that off my chest first

    those 5.7litre designated motors were capable of some wonders if one could set them up properly with a reversing kit and a 350 olds topside you could power a rail dragster and be a contender in your class

    i owned four of them, each sporting a diesel engine when i bought it. and i went out and bought a gas engine to replace the diesel when it popped head bolts and blew a head gasket or when it started to leak fuel or when the injector pump crapped out i got them so cheap that it was ridiculous people were for throwing them away when they got so disgusted with them

    the first one i owned was a ninety eight olds i put a hi output 350 from a 77 cutlass in it and it delivered 18 mpg at highway speeds i would still have it today but the battery blew up one morning after i left for work and it was fire damaged too much to repair

    the third one was a delta 88 i bought it from the back of a small lot for scrap price plus $50. after multiple problems with injector controller and expense for injectors, i had a runner and i ran it 80 mph for a gillion miles but i never crowded it up to that speed i was into smooth sailing the motor finally blew a head gasket and i had my brother in law install the gas engine i had stashed it went another gillion miles with a gas engine and finally got so ragged that even i was ashamed to be seen in it so i gave to my son for parts for his race car

    what i have figured out about diesel is just this: if you do not know anything about diesel engines, they will cost far more than they are worth if you try to use one especially if you try to get it to operate outside of its comfort zone

    that being said, the newer vehicles have sophisticated control systems that can idiot-proof the vehicle and create a symbiosis of sorts to eliminate a lot of this discord

    and one more thing gm has switched to an isuzu diesel for their diesel applications just as ford with international and dodge with cummins looked to experts to keep their good named untarnished

    Like 0
    • 68custom

      actually after 2010 Ford was Making it,s own Ford V8 diesel boat anchors. A steel of an option at over 8K!

      Like 1
  22. Keith

    Had a chance to pick up a nearly identical one this spring. Coupe, diesel, kind of a butter-cream color… $900. Was leaking oil like a sieve but it ran. Didn’t bother determining where the leak was coming from, since it was abundantly clear the guy wasn’t open to negotiation, and it just wasn’t worth $900 to me.

    Probably the most memorable part of the whole experience was when I started it. For some reason I found it simply hilarious, hearing the clatter of a diesel coming from under the hood of a B-body. Kinda like finding a dog that meows, or a cat that can bark.

    Like 0
  23. jps311

    Parents had a brand new 1980 delta 88 royale diesel. Nothing but problems. Finally blew up around 50000 miles. Then dropped a 307 out of a wrecked cutlass. Car went another hunfred thousand miles aftet that. Ate up quite a few trannys too. But it was like driving on cloud

    Like 0
  24. pappy2d

    My Dad bought a new Pontiac GP in 1980, with this engine. It was a garage queen, but still failed regularly. Batteries, fuel pumps, starters…. If memory serves, the wiring harness vaporized 1000 miles from home. I’m sure the gas V6 of that day would out perform the diesel. It was the financial trifecta. 1. Cost more than the gas engine new.
    2. Maintenance/repair costs were off the chart. 3. Compared to the gasser, they had no trade in value.

    Like 0
  25. Jim

    I was a technician in a GM dealer from 78-81 and because I had diesel experience I got every one that came through the door. I changed countless camshafts under a program from GM, they were buying cam blanks from South Korea and the metal was horrible, if the oil level wasn’t maintained, wrong oil was used the main bearings turned to crap and the bottom end came apart, God forbid if the geadbolts weren’t re-torqued on time or it overheated the head gaskets let go. It was based loosely on the Olds 350 but executed horribly. GM lost a ton of future customers due to that fiasco, eventually they had Detroit Diesel design the 6.2l v8 for the light trucks but continuing to leave their head in their respective butts and being in a hurry made it naturally aspirated which the aftermarket went wild selling turbocharger kits, the upgraded 6.5l finally came standard with turbos. It’s amazing to think a company that owns Detroit Diesel would’ve screwed up so badly getting into the automotive diesel market. For the guys about to scream about the 6.2l the govt/military purchased in excess of 300,000 vehicles with that engine and used a lot of them for 20yrs. Those were bad days for American car companies.

    Like 0
  26. jimmy

    My dad said my grandmother had one and it was the slowest thing on earth. Their driveway was steep and if you slowed down going up you’d have reverse back down the driveway and get a running start it was so slow and under powered.

    Like 0
  27. 427Turbojet 427 Turbojet Member

    In the late 80’s I bought an 82 Caprice wagon for $200. 00 – 5.7 diesel with a blown head gasket, but a very nice clean car. Also bought a 72 Olds 98 with a 455 and 400 turbo. Combined the 455/400 with the Caprice body, put 15 X 8 Chevy van rally wheels on it. made a terrific trailer tow vehicle. Ran it for many year until it just wore out.

    Like 1
  28. Brian Joseph

    In the mid 80s i converted a fair amount of gm 260 and 350 diesels over to gas engines
    Gm gave up on these engines and the best way to fix them was to go gas..easy swap.

    Like 0
  29. John b

    I understand if you wanted to convert to the 350 gas engine, it was best to use the olds block because all the brackets bolt holes matched up.

    Like 0
  30. Brad

    So, the diesel engines in the Chevy M-1008/1009 engines weren’t GM? I didn’t know that. They were very reliable, in all driving conditions.

    To answer your question about the plastic surrounds around the bumpers, I believe they were know as “filler caps”. They were designed to collapse or bend if one of the 5 mph bumpers made contact with something, keeping the body safe(r) from denting. After several years, they loose their elasticity, and crack or break. A common problem with GM products, especially with the one between the back bumper and the trunk.

    Like 1
  31. Bryan

    I remember when the 5.7L (350 cid) diesel was introduced in 1978… my best friend’s parents bought a beautiful Delta 88 Royale 2dr. By the way, I think these downsized (starting in 1977) Bonnevilles are very nice looking cars!

    I distinctly recall a Motor Trend article at the time that noted GM’s claim that the average lifespan of their diesel was no more than their gas engines (roughly 100k miles). This struck me as odd, knowing that other diesels of the era were built to rigidly high standards (due to 22 to 1 compression, etc) and were known for long life. GM marketed their diesel on the strength of its economy, not its longevity.

    Like 0
  32. Peter

    Wow–having owned one of these engines, in a Olds Vista Cruiser, and also read a comprehensive Hemmings article on the Olds 350 Diesel, recently, which agreed with my positive experiences, I’ll have to write more, later–I just don’t have time now, but want to make sure I don’t lose track of this thread.

    But the Olds 350 diesel was NOT a “converted gas engine,” as the more knowledgeable here have stated. (I used to think it was merely a gasoline-based engine, too, until I read the Hemmings article.)

    To the nayesayers: please, proceed. I find it amusing, in light of the (up to) 30mpg ours got, and it’s effortless, 80mph (overdrive-equipped) highway composure (though it may not have got quite that high of mpg at 80mph–but it was impressive mileage, at ANY sustained highway speeds, especially pushing the slimmed down, but still full-size, Vista Cruiser wagon.

    I’m seriously interested in this Bonneville, btw…thanks, barnfinders–and “Scotty,” in particular!


    Like 3
  33. juan

    I guess GM needed a little bit of advice from experienced diesel companies or more test time, these engines had some defects that could ve solved with a little more engineering, the head crakcs or blow head gaskets can be solved putting more bolts on the heads (not random, of course) but in some cases when you do it crankshaft cracked (sometimes, not always), maybe a more strong crankshaft will be needed and most important a REAL fuel filter with water trap., water ruins injection pump and injectors for good.
    Deffects solved or not I can testify that these engines didn´t take beating, they broke down or didn´t last much.
    About camshaft, never heard of problems with it.

    Like 0
    • Dave Wright

      That is one of the most rediculious comments of the year……..GM is the largest Diesel manufacturer in the world. Most locomotives, tugboats, pumps, generators, buses and trucks manufactured from the late 30’s on used GM Diesels. Look up EMD and Detroit Diesel, a huge percentage of the diesel equipment we used to win WW2 was GM powered. My best buddy just bought a modern Bus/RV conversion with a 600 hp Detroit. My largest tug boat has a 2000 hp GM diesel built in the early 50’s. It has never missed a beat and the hr meter reads over 99,000. I might agree that the engine being discussed is not there best effort but not for lack of experiance. I owned a 80’s Coupe Deville diesel that was a great car, but I am a diesel guy and it had been owned by an old customer of mine with influence and deep pockets. It had the engine replaced by an upgraded version when it had 10,000 miles. Also, I do a lot of miles, the car was usually driven 10 hrs when it was started. Diesel like to get warm, run at constant RPM………not how the average sedan driver uses a vehicle, as for being a converted gas engine, some of the best Diesel engines on the planet are built in both gas and diesel versions. The Mercedes 4 cylinder engines have always been built in both gas and diesel versions. The question is were they diesels made to run on gas or gas made to use diesel………then there were the Military multi fuel engines, they had diesel injection systems on one side of the block and a carburator, distributor and soars plugs on the opposite side. You could choose whitch one of a half a dozen types of fuel to operate on. We usually ran them on diesel because it gave us the most power………diesel has more energy per gallon than gasoline does.

      Like 2
  34. Bryan

    I’ll agree that the 5.7l diesel was not a converted gas motor. It was, however, an under-engineered effort released just before the second gas crisis of the seventies caused the collapse of the ruling Shah’s government in Iran.

    Initially, these GM’s diesels were perceived as a godsend to the consumer. These rather anemic automobiles could offer full-sized comfort with excellent economy. Diesel appeared at almost every gas station overnight thanks largely to GM’s success.

    By 1981 GM was selling 310,000 diesels a year! Just 3 years later the GM diesels were removed from the market as sales stalled because of reliability problems and dropping gas prices. A close family friend owned a car dealership at the time….they wouldn’t touch a diesel trade-in at the time…of any make. GM’s foray into the diesel market effectively damaged the north American passenger diesel market for the next 20 years!

    Like 0
  35. Steve

    Well she sold for $3,200: 8-track, velour upholstery, diesel engine and all. Does this seem about right to you guys? To me, a thoroughly forgettable era of cars, those GM diesel passenger cars. Most of all, I remember getting stuck in traffic behind them on freeway commutes and having to endure the stench of the black diesel fumes. Oh and the clatter. I do remember how they would clatter so loudly. Glad those days are behind us.

    Like 0

      Pretty sure it didn’t sell, it had a “Buy it Now” price of $3200 and I don’t think any one bought it, the listing just expired.

      Like 0
      • Steve

        Ah, my bad. So no one bit on it at that price. The diesel must’ve scared ’em off?

        Like 0
  36. Doc1

    Head gasket problems. The fix was to use studs instead of bolts

    Like 0
  37. JBL

    Careful…. these were gasoline engine blocks, converted to diesel.

    Higher compression and dynamic stresses were known to punch a hole in the cylinder walls.

    Like 0
  38. nessy

    Oh, I just had to jump in here.. I have two GM diesel cars from this era. A beautiful 1980 Cutlass Supreme Brougham with T Tops and a spotless 1982 98 Regency Brougham, both still have the original factory diesel engines and both have been in my family since new. Not one lick of trouble with either car in over 30+ years. Oh, they have alot of jump off the line and still pull ok in the mid to high range. The cars are not slow from a start due to such high compression, something like 22 and a half I believe. With compression like that, they are impossible to be slow off the line. If you know how to treat a diesel, you will not have problems. The problem was the owner/drivers. A diesel is not the same as a gas engine and must be treated with more care. Here are the 6 most important rules for a diesel.. 1st, when first starting the car, let it clatter and skip around until it idles down on it’s own, 2nd, do not over rev the diesel ever, 3rd, do not mash your foot to the floor off the line, it’s not designed for that, 4th, change all fluids every 2000 miles or less, 5th, plug in your engine block heater if it’s going to be below 50ish, and last, always check your water in fuel light, if it does not go off, do not start the car. I speak from facts since I have been around the GM diesels since they were introduced. My cars get 30+mpg on the highway…. I love my diesels!

    Like 5
    • Dave Wright

      Well written and generally good information. The high compression part is not correct as far as acceleration. Diesel engines require high compression to operate. They have no spark plugs and the explosion in the cylinder is caused by rapid compression of the fuel air mixture, it creates heat that causes ignition. It really does not relate to compression in a gas engine.

      Like 2
  39. Bryan

    GM handed 60% ownership of Detroit Diesel to Penske Corp in 1988 (Roger Penske became the CEO). Detroit Diesel was bought outright by Daimler-Chrysler in 2001 and is still owned by Daimler AG.

    In fact, since 2001 even GM’s Duramax truck diesel is made by Isuzu, truly a global giant in diesel engines. International still makes Ford’s Powerstroke truck diesel.

    Too bad that GM’s decades long ownership of Detroit Diesel did little to make the 5.7L better engineered or more reliable…they should have known better. Of course, this was the GM era (or soon would be) of V8-6-4 and HT4100 Cadillacs, weak Metric 200 transmissions, and problematic digital dashes.

    Sounds to me like GM hasn’t been a player in Diesel technology for a quite a long time.

    Like 0
  40. Scotty Staff

    You guys are unreal! The vast wealth of knowledge on this website is amazing!

    Like 1
  41. Scotty Staff

    Auction update: this Bonneville sold for $3,200!

    Like 1
  42. Philip

    Lots of good info here from those of us who were there in the dealer shops when these were new. Studding the block prevents quite a few issues, notably the head and gasket problems. You could get a stronger crank/ rotating assembly that will survive the abuse of diesel compression as well. The biggest problem you were left with was injectors, pumps glow plugs and modules. If you knew your stuff finding a bad injector or replacing the pump was child’s play and payed quite well once you figured out how to flat rate the job without any issues. The first 350 diesels were indeed gas motors and proved to be weak and unreliable. More often that not the early engines failed catastrophically. The later 5.7 diesels were far better, and enjoyed moderate success provided the customers treated them right and followed the rigid service requirements to the letter and mile. There were a surprising number of these that didn’t get converted, though we did convert a lot between 1980 and 1984/5. Many were still out there with the 5.7 version in them up to the late night nineties with scads of miles on them. Proper oil, plugging them in, and good fuel helped, as did letting them warm up and settle down. Diesels are not happy cold, and like to stay warm. Of course glow plugs were problematic as well as was the module. Eventually that was straightened out, but all of this came too late to save GM’s credibility in the area of consumer diesels. The 6.2 for pickups and so forth were also rushed into the market with tons of reliability and catastrophic failures, blown/ cracked heads/gaskets, rotating assembly failures and the typical injector pump and glow plug issues. By the time the 6.5 turbo diesel most of the issues were solved, with injectors and pump issues being far fewer and furthur between, as with glow plugs and modules.

    Speaking of the V 8 6 4 motors, I can remember them coming off the Anchor Freight trucks with burnt valves among the plethora of other issues. Not one of the better designs or ideas from GM, the solenoid deactivated valves didn’t work well and..they were about 30 years too early for multi-displacement engines. The technology just wasn’t there, though the early throttle body injected DFI cars ran really well and had a lot less issues than you would have thought with the technology being as new as it was. The early CCC feedback Carburetted cars could be nightmares especially all the pollution controls sucking the life from the engines to begin with. No one had any real experience with them, school helped but therr were a lot of gaps between STG and the dealer level Tech’s. lots of cursing and frustration .

    All of these screwy designs ended up being converted in one way or another under programs Zone level management overides, or special policy. Yet another reason I left Chesapeake Cadillac back then for a Chevrolet dealer. I was tired of all that special policy and extended warranty work, since Cadillac had the double whammy of diesels and V 8-6-4 cars always filling the shop and everything possible was being squeezed on to warranty tickets with little straight time. Not the best of times for a flat rate technician. Wasn’t long after that 12/12 went to 3/36 and beyond. The handwriting was on the wall and the days of making killing working for the dealer were over. If you wanted to make an easy living and earn 1k or more a week, aftermarket was the way, A lot less hours too. I nearly doubled my salary the first year in the aftermarket from what I was making at GM dealership. From there was no way to go but up especially with knowledge of these cars most didn’t have. And I could charge accordingly for it.

    Like 0
  43. Joe

    I dropped a 350d into my 1979 Formula Firebird. TH350 with no lockup converter and 2.73 gears. I actually got 48 mpg out of that car!!! Got jobs at 3 different dealerships with that car. My parents had purchased a 85 Olds Custom Cruiser wagon and consistently got 28mpg out of that barge. Ive had allot of these and loved every one of them. They were by no means a hot rod and you needed previous experience of driving diesels to make one last. Head gasket fix was to o-ring the block the same way that they did for nitros injection. Drag racers are doing this using the stock injection and making around 500 hp.

    Like 0
  44. Joe

    Engine, You can not blame a lemon for being a lemon, WHY !!! Because it’s a LEMON DUMMY !

    Like 0
  45. Duaney

    I drive a variety of Olds 5.7 diesels almost daily, no failures, no problems, and after experiencing the Olds diesel, I don’t have much desire to go back to the gas version. They start right up, no vapor lock ever, seem to get double the fuel economy over the gas. I agree with some of the above comments, most failures are due to poor operation and maintenance by the owner. Also, catastrophic failures are due to water in fuel, so failing to drain water out is critical. Most of my diesel have an aftermarket water separator, I do slam GM for not including this on all of them, instead of the fuel in tank warning system.

    Like 0
  46. john

    My dad had this exact same car. This beast wouldn’t start in Michigan winters, he had to plug it in, and that diesel broke, often. He didn’t have it but for a year or two and it was gone but forever in my memory, the sound, the smell of that diesel.

    Like 0
  47. Glenn Weisel

    What a beautiful car ! I came from a family very loyal to General Motors products. Throughout the family the only divisions we never owned were Hummer and Saab. I had a light blue 1980 Olds Delta 88 Royale with a padded vinyl landau top just a bit darker than the body. Oh yes I forgot to say it was a diesel. I bought her used from Merrie Cadillac Olds in Doylestown , PA . This was a beautiful car, one of my favorites to this day and I loved this car. Most of my driving was in the highway and turnpike catagory . We only suffered a failed transmission around 70K miles, never an engine problem. It was a Diesel engine from the Pontiac division as identified by numbers in the VIN. UNFORTUNATELY , we met up with demise in an accident when the car was totaled. Later we added a 1984 Olds Delta 88 Royale Brougham , burgundy with padded vinyl landau top and matching velour interior. This 1984 model was also a 2 door coupe but with a standard 305 V8. BOTH of these cars were beautiful cars , exquisite design , and very comfortable driving cars. I wish I had one of these cars today . Our present day cars are lacking in design and style however they are much more fuel efficient. Considering the price of our current cars, what ever happened to design ? No wonder many have given up on GM and are seen driving Kia and Hyundai models. What does the future have to hold ?

    Like 1
  48. Boston gene

    1981 Bonneville Coupe Brougham Diesel with a hlaf padded landau top. WIth the Honey Comb Wheels and the plushes deep Biscuit deat pattern I’ve even seen on any car. Matching marroon color. Why did I beg for this diesel over the gas V8??? because I was 19 in 1981 and i traveled to work 45 miles a day. The car was so under powered. The fuel Injectors blew in a month, Over Drive also went out. GM Had my car for 4 months trying to fix it. Leaving me with nothing to drive to work in, I paid the extra $1800 for the Diesel Feature.

    Like 0
  49. The One

    The interior guarantees a major wedgie..

    Like 0

    I know I’m 4 years late… but I’m thinking I want this thing. What a nice boat of a cruiser. I think I could deal with the Diesel… $3200 was a lot more 4 years ago. Amazing how things change

    Like 0

Leave A Comment

RULES: No profanity, politics, or personal attacks.

Become a member to add images to your comments.


Get new comment updates via email. Or subscribe without commenting.