Olds Diesel Power: 1980 GMC Sierra Classic 15

Certain topics should not be brought up at the dinner table unless you are armed for verbal battle. I have a friend that will not discuss “religion, politics or motor oil” with anyone because of the heated debate that will usually ensue. I have witnessed this same type of debate happen when the topic of the Oldsmobile built diesel engine is brought up.  A large majority of people despise this engine for the reputation it has, but there are the ones that are very passionate about it and feel the reputation is unjust. Lets take a look at this unusual 1980 GMC pickup found here on craigslist in Newfield NJ for $7,995.

The truck is in nice shape for a 1980, all of the trim looks intact and the body looks fairly straight. The paint may be a bit of a 50 footer as the color has been changed from white to dark blue at some point in the trucks life. The long bed is not the most popular but, it is practical as well as the tool box.

The interior is in good shape as well, the color combination of white, red and dark blue is a bit odd but it could be worse. This Sierra Classic is well equipped with air conditioning, power windows and door speakers. The door panels and bench seat are both in good condition.

Mileage is listed as 65k, but the truck is equipped with a 5 digit odometer, judging by the wear on the interior the mileage is probably accurate. From the pictures rust does not seem to be an issue with this truck. The ad states the truck runs and drives excellent. Under the hood is where things get a little out of the ordinary. This GMC is equipped with the 5.7 liter Oldsmobile designed diesel V8.

This engine was produced from ’78 until ’85 and was used in many GM full size cars and light duty trucks. Producing 125 horsepower, it was no power house compared to todays diesel engines. The Olds oil burner were plagued with problems from the start, most problems related to the head gaskets and fuel system. I have heard the engine can be made quite reliable with the proper updates and service. Is there anyone out there that has a good story relating to this piece of General Motors engineering history?

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  1. 68custom

    looks the the windshield is cracked which is a common problem for these but at that price it should be replaced. I have heard the diesel is fairly reliable as long as it has fluid changes and always keep a spare injector pump handy. kinda looks like it should be sitting on the lot at a pay here pay here,. worth maybe $3500 IMO!

    • 68custom

      whoops! buy here pay here!

  2. flmikey

    No, I do not have a good story…but I got a couple of bad ones, and so do most people that purchased this grenade of an engine…I say most…I’m sure there were one or two lucky ones…

    • Greg

      My father chased this engine for years. Head gasket went 3 times. Gutless wonder. Couldnt tow a shadow. Sentamental value at best. Great piece.

  3. nrg8

    My 80 C10 that has a 1991 goodwrench rebuild in it, blew a head gasket last summer. Used it as a daily for 15 years, then summers then on. Did one IP rebuild, and oil changes. Good commuter, pulled a ski boat no problem. I drove it hard, and as long as oil changes get done and the cooling system is functional they are pretty solid. My son wants to put new gaskets in and drive it when he gets his licence. Been looking for a 70 or so rocket to change it up a bit. Either way yep early ones were crap. People were on to the 6.2 by the time the bugs were ironed out and you could get them cheap.

  4. Miguel Member

    I am surprised there is still a truck out there that hasn’t had the engine exchange done already.

    When did the diesel become a positive as far as price goes when it has always been a negative?

    • nrg8

      Unless the vehicle equipped with said diesel is immaculate, even then it always gives tons of haggling room. But this scenario, only seen one on ebay 6500 miles it went for 24k , this one looks tired, too much$

  5. KKW


  6. Bob S

    I have a buddy that put 150,000 miles on one in a GMC 3/4 ton (sorry, can’t remember the year). He pulled a 5th wheel all over the US and Canada, and was well aware of the potential problems associated with these engines.
    The fuel pump finally failed, not catastrophic, but enough to require a repair, at which time he traded it off.
    Another friend bought a used truck with this engine for peanuts, and put a big block in. Problem solved.

  7. Ron

    I had an 80 Olds 88 which I bought with a Goodwrench engine in it with about 45,000 miles on the car. I ran it to about 100k and then the tranny went. I put in a new tranny and sold it. The only issue I had besides the Tranny was the injection pump which I changed. You could floor that car and your passenger wouldn’t be the wiser. But overall I liked it.

    • Bob S

      Your comment reminds me of a Toyota BJ40 that I owned. You had to plan a pass a day in advance. You never had to worry about snapping your neck when you accelerated.

      Another thing I forgot to mention, was that I loved the hydravac brake system that the Diesel trucks had. I assume the Diesel cars had the same system.

      • Ron

        Lol. Yes it had hydraulic assisted power brakes. Also at idle the diesel of course was a little clackety clackety but once the RPMs increased it went into a really smooth buzz. Very nice sound

  8. Dave

    My parents bought a new 1981 Delta 88 Royale Brougham. My father maintained it right to the book. At 50,000 miles, you could not keep enough oil in it due to blow by…GM put a new motor in for free, and he drove it another 50k before curbing it.

  9. Ted777

    Had an 1982 shop truck with the diesel used to run the heck out of it remember I could almost get to 100 mph in it but I liked the company’s Elcamino with the 350 4 barrel better than the oil burner.

  10. Richard Jefferson

    I had a 1982 Chevrolet Impala wagon with the Olds Diesel. The engine was amazing. Bought in 1986 at 100k sold at 250k. One Sunday with family of 8 going to dinner. A engine oil/radiator cooling line burst and pumped out the oil. Too hot to stop the a/c car I drove 12 miles to the restaurant with engine pounding. Repaired the problem and had the car 2 more years. Tough engine. rj

  11. JohnBoy

    Take that 350 DX block and slap a set of Oldsmobile 403 head’s on it and now you’ve got a little sumpin sumpin. A high compression roller lifter gas burner that could embarass z28 Camaros and mustang’s. You have to run higher octane fuel because of the compression. 🤙

    • nrg8

      Just a set of 403 heads? Point me to that link. I was under the impression to use the dx block for a gas power house required a little bit more than that.

  12. Earl Stephens

    Bought a 79 Olds station wagon w/5.7 diesel in 1983 for $2700 w/56,000 miles on it. They had a 30 day guarantee on the engine and drivetrain. I insisted on a 90 day, turns out 30 was plenty. Got a new Goodwrench Diesel we put almost 100k on before we had to put a rebuilt injector pump on.Put another 15k on before head gaskets blew. Still a nice cheap ride and good value. But I wouldn’t want another.😅

  13. Mark

    We had an 80 gmc. If it went colder than 50f it wouldnt start. Horrible .
    Also had an 80 olds cutlass withe the diesel. Awesome car. 32mpg. Took awhile to wind it up. Keep your foot in it and it wasnt bad. The problem we had was the oil pump driveshaft would wear the edges off of the shaft and spin. Lost oil pressure. $6 part. It happened at 40k and again at 90kmiles. Most of thise engines were lost for that reason. Most people just kept driving when the light came on. Put a set of glasspacks on them and they sounded great

  14. Wade anders O

    Drove a delivery can with that engine in it loved driving it company maintained the boss insisted on new fuel filter every 3000 miles

    • nrg8

      Yep, terrible design the rectangular metal filter had the line in going to the top left corner. The line to the IP was on the bottom right. Water sinks to the bottom when you turn em off and the next start up it gets pushed into the injection system, unless it freezes. Your boss is a smart man.

  15. Steve


    • KKW


  16. Basshnter1

    Had two of these in station wagons.
    Both were later engines after most of the bugs were worked out.
    I did have terrible issues with glow plug controllers.
    These were incredibly slow but a 4000 lb car that got 25 mpg, not bad.

  17. Charles

    Had an Olds wagon in 78. Blew two sets of head gaskets and one injector pump. Told wife to take it to dealership and get something else and under no circumstance was she to drive back off the car lot in the Diesel.

    Had a warrenty claim for first blown gaskets shortly after delivery. Picked up car after repairs and was billed for all new belts. Found out the mechanic cut them off with his pocket knife. Dealership ate that charge since GM denied it.

  18. Brian

    I used to work on plenty of them. I was a GM tech at a Chevy/Olds dealership. Replaced a whole bunch of head gaskets and bolts. Also injection pumps. Then we started replacing the entire engines with the DX block Goodwrench replacement. By the time GM came out with the DX Block they actually had one hell of an engine that with a little injection pump advance they would actually smoke the tires! If it has the DX block it should have plenty more miles left in her.

  19. JimmyJ

    Worst diesel ever.
    I know square bodies are going up in value but a long box 3/4 ton with this junk motor is a tough sell at half the price..

    • Andrew

      Actually, I agree with you on everything except on the engine: a long box 2wd GM square body isn’t anything particularly interesting, but having its original Olds Diesel still in it is what makes it a rarity – and somewhat collectible.

  20. JimmyJ

    Oops half ton,still junk motor!

  21. Bingo


  22. LAB3

    $8k for what to me is nothing more than a work truck is hard to see. Originality would be this trucks drawing card and this one doesn’t have that.

  23. Howard A

    As the owner of a similar truck, it’s not junk. Ok, the diesel took some special care, something most previous gas job owners knew nothing about. The diesel was a good unit, 2- 300g’s was not uncommon, but required strict maintenance, and you had to respect the motor. No, they did not have the response a gas motor has, and you have to “baby” a diesel, especially when cold, or on long pulls. But if you kept your foot out of it, they did produce better fuel mileage than ANY of the gas jobs ( mid 20’s easy), their big selling point. Depending on the condition of this motor, it may be best to swap it out with a gas motor. Still a nice truck, regardless.

  24. Frank

    First gen. of the Olds diesel had issues … the block had a D cast into the side. The second gen. has DX cast into the side which addressed the head sealing problems. When you had the injection pump rebuilt be sure to have brass retaining ring instead of the Mylar that will eventually break, a common problem on all DB2 Standadine pumps … 6.9, 7.3, 5.7, 6.2….

  25. Gay Car Nut

    While I’m all for a diesel engine for a truck like this, I’m not so sure I’d want my truck to have an Oldsmobile 5.7 litre diesel engine. For a truck like this, I’d install a 6.5 litre Detroit Diesel Turbo, or a 6.6 litre Duramax, if it fits under the hood.

  26. geomechs geomechs Member

    Having worked for a GM dealer when the 350 diesel was in full battle regalia, I can safely say that the vast majority of the negative comments are unfounded. People rushed toward them because of the better fuel economy. They didn’t stop to think that a diesel requires a completely different mindset to operate properly. A diesel doesn’t like to start and stop; it wants to get up to temperature and WORK. People found that out the hard way. The 350 diesel was designed to pull/haul a certain sized load; a pickup with a 9ft overhead camper and pulling a 4-horse trailer was a serious overload (Sorry, chum. GM gave you a new engine under warranty but it isn’t going to look after your second broken crankshaft.). GM service departments were the Deer In The Headlights when a diesel came in. No matter what the complaint was the injection pump (and injectors) was pulled and sent away. A gas engine popping back through the intake indicates that an exhaust valve isn’t opening, and you start looking at the valve train. Why was it when a diesel came in that you replaced the injection pump and injectors THREE times? I heard the frustrated owner’s car drive up to the front of our dealership and told him that he probably had a bad rocker support, which it did.

    Camshaft failures? Yes, we had a lot of them, mostly SBC 350s, Buick 350s and 455s, Pontiac 455s, Chevy 454s, Chevy 292s, and SBC 305s. A few 350 diesels too. I might add that Ford was experiencing camshaft failures and Mercedes was having an epidemic of failed camshafts on its 300Ds. This happened during a time when the API changed the spec from SE-CC to SE-CD. After a whole bunch of pissing contests, the API put most of the zinc back into the formula and came out with Spec SF. Miraculously, problem solved on ALL cases.

    In short, and I will mention that I’ve argued with the malcontents till the cows came home and left again, the 350 diesel got a bum steer. MB had more failures per capita than the Olds yet Olds managed to take all the blame. I would have no qualms of owning and running a 350 diesel. In fact I’m looking for an ’80 or ’81 Eldorado that’s equipped with one. And I wouldn’t be afraid to take it for a round trip around the country….

    • Gay Car Nut

      Perhaps someone should’ve reminded buyers that when purchasing their first diesel powered vehicle.

  27. Doug

    I worked for GM, and in the early 80’s we were shipping hundreds of new crate diesels to the dealers every month as replacements for failed engines in Northern California, Nevada, & Utah. After a while, GM started offering to have the dealers replace the diesels with “Targetmaster” 350 gas crate engines as an option, since many owners didn’t want anything to do with the diesel ever again.
    One of the problems with the diesel was that they were built in a gas engine plant, and using tolerances that were acceptable for gas engines, but not tight enough for the extra pressures generated by diesels. So, while a small percentage of engines may have been assembled with parts that had the proper tolerances for a diesel, purely by random chance, the majority were not going to last.

    • geomechs geomechs Member

      Strange. I never heard of any program offered by the General to replace the diesel with a Targetmaster. I do remember some complete diesel engines showing up on a special promo through GM. A friend of mine got to thinking that original engine in his ’78 pickup was getting long in the tooth so he bought a complete engine and dropped it in. He brought me the injection pump off the original engine and had me change the governor over to a full constant-speed so he could use the engine to pump irrigation water on his 60 acre hay field. He installed the water-cooled exhaust manifolds and put it to work. Ten full seasons before he pulled the engine offline and converted to 3-phase electricity.

      The closest I ever heard to a program to repower the vehicles was a bunch of surplus 350 and 455 industrial engines that showed up on the market. There were some engine/parts shops around Great Falls and over toward Billings and Havre (and even into Canada) that offered ‘new’ 350 and 455 gas engines to replace that ‘troublesome’ diesel. What they did NOT say was that the gas engines were built to run on NATURAL GAS/PROPANE and required a different carburetor, and an actual fuel pump, which was followed by a different camshaft and a total recurve of the distributor. The fuel economy was atrocious and the power wasn’t much better.

  28. Ron

    I had a 79 350 has in mint condition about 85 and 33,000 Miles,remember the cam mushrooming,but gm looked at the truck said it was reacurring problem and replaced it that many years later 3/4 Tom only problem I ever had with it

  29. JimmyJ

    If theres an argument about engine reliability it probably isnt reliable…
    U dont hear this about 350 chevys and slant sixes.

  30. Comet

    I may be crazy, however I seem to remember an outfit offering “conversion” kits to change the existing diesel engines into gas engines. Does anybody else remember these kits?

    • Norman Wrensch

      I did that changeover once, just put the gas top end on a diesel short block, ran good. I did it for a friend and he ran it a long time. But I never heard of a kit to do it

  31. Taildraggn442

    Well every comment has a good point, but I currently have 5 350 diesel engines and blocks. Two being used today. These motors I’ve never heard any good about but I still am buying and hoarding them. One motor is still a diesel and though I’ve put money in the motor it serves it purpose in an s10 I use on the farm. Has no power or towing capacity but I like it. They were a good idea. Just not thought out well. The second motor is a gas conversion. These motors done right will stomp most race worthy small blocks. I know cause that’s what’s i n my 1965 olds 98 hearse/ ambulance package. I got the car as a kid and that’s how it became what it is. If it were know I would of left it alone. Any ways my little diesel block is now 440 ci 787hp 1173tq. And bring that car might I add is only 3882 with me in it in the high 9’s. This motor seems bulletproof. Never had any major problems except finding parts fast enough. Now it has twin 86mm turbo’s. It was 3300hp on 35lbs of boost.I’ll let you know how it holds up. All in all if you want a 350 diesel block get it for what it is not what you think it would be. They would be great for a daily in my opinion. They are not hauler’s. Great putters. I love my s10. If you chose to convert it do your research they can be amazing. I’m sure there’s not many people out there like me that got lucky with one. It really depends on what you want it for. As nobody wanting them where are they all at I’ll buy them.

  32. Duaney Member

    For in the USA, changing the diesel to a gas engine violated the EPA standards and was illegal, still would be illegal today. You could get away with it if you were in an area with no emissions test. I operate several 5.7 Olds diesels regularly and love them, very dependable and no failures of any kind. I will say that GM underestimated the diesel fuel contaminated with water, and underestimated the intelligence of their customers who didn’t drain the water from the fuel tank and didn’t change oil when required. Catastrophic failure occurred when water reached the engine.

    • Gay Car Nut

      That can certainly be a problem. Every engine requires maintenance in order to run reliably, it doesn’t matter if it’s gas or diesel. I remember back in the 1980s, when car makers would advertise their cars as being “trouble free.” or they would say that their cars were “maintenance free.” Even though I was just a boy at the time, I knew that was a load of B.S. I knew that there was no such thing as a car being maintenance free. However well-built something is, it still needs maintenance in order to continue running reliably. :)

    • geomechs geomechs Member

      A lot of problems could be based directly on operator error. I remember—after getting so fed up with a customer that I no longer cared what waves could be made—telling a customer that the stickers on top of the batteries, reading: ‘Maintencance Free,’ referred to the batteries ONLY, not the entire vehicle. He stormed out and cried on the boss’ shoulder. The boss came out and ripped me a new one. Then we all went back to work. The customer took his ray of sunshine to another dealership for a couple of months before he came back….

  33. Jerry

    But it has red, white and blue interior!!!!

  34. Zapp

    Nice truck, but $7995 is a wildly optimistic asking price. Looks like a $4000 rig to me.

    Chances are, having run for 38 years, the diesel 350 in this GMC is one of “the good ones”. I wouldn’t hesitate to make it mine, if the price was right.

  35. Big J

    Junk, lol. Thats people who didnt understand its purpose & abused it. Fuel economy and that was it. They should have never put it in a truck, thank Christ the 6.2 came along. I run an 82 Caprice diesel as a daily driver, only issues was a broken valve spring and IP pump in 230k miles. Doesnt look pretty, not fast, & cost nothing to run. Just more $$$ to dump in the tank of my HellCat

    • Gay Car Nut Tacoma

      I have to agree. The 5.7 litre diesel was fine for cars. But for pickup trucks and SUVs, it would have to be either the 6.2 litre diesel, or the 6.5 litre diesel.

  36. Big J

    Yes, its a popular race thing to do cause of the block being stronger

  37. juan

    Please correct me if I´m wrong but I did a huge research about these engines and their problems and the conclusions of years of asking to mechanics and owners were this: the first one was the desing was made from a gas engine, the heads, engine block and crankshaft were not prepared for such compression and broke but this was the least of their problems, the first was the fuel filter wich was too permisive and with no water trap (GM´s BIG mistake N°1), you put a REAL fuel filter and problem solved, the headgastets blowed whitout warning, you put better screws and drill new holes in specific places and put more screws and problem solved, the crankshaft and block were difficult to solve but if you don´t abuse 24/7 of them was more a question of luck.

  38. Bryan

    I had friend who owned one of those trucks. It was a 79 model super good looking truck. The eng blowed a head gasket. My friend just happened to own an Oldsmobile car with the 350 gas engine. Dropped it right in the engine run beautifully and problem solved.

  39. Wayne

    I would love to get a hold of a dx block for a gas conversion but not having much luck.

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