The Cadillac Seville was introduced in 1976 so the company could appeal to a wider range of buyers (the DeVille tended to attract an older crowd). To improve fuel mileage and maybe lure Mercedes owners, the car came with a standard diesel V8 engine in later years. The seller has a 1980 edition with the Oldsmobile 350 cubic inch diesel, which has an older repaint in a 1981 color scheme. Having owned it for 10 years, the seller is ready to move on to something else, so it’s available in Forks Township, Pennsylvania, and here on craigslist for $3.700. Thanks for the vintage tip, Tony Primo!
Through Oldsmobile, General Motors developed a 5.7-liter diesel engine that was in use from 1978 to 1985. Rather than being an all-new design, GM modified the existing gas-powered 350 V8. It was developed during the mid-1970s energy shortage era as a means of getting better fuel economy in larger cars, but that didn’t seem to pan out as expected. The engine became known to have reliability issues. Chevrolet used it in the Caprice for a time but backed away after a couple of years.
The second generation of the Seville (1980 to 1985) employed “bustle-back” styling in the rear. It also used front-wheel drive, as deployed by its cousin, the Eldorado. Though the diesel was standard and probably went into most of the early 2nd gen Sevilles, you could opt for the gasoline-supping version as well. Third-generation Sevilles (1986-on) dropped all of that. The seller has owned this 1980 version that he/she’s been “playing with for 10 years”, which suggests that the seller, too, has had enough of Olds diesel engines. Shop manuals come with the sale.
This vehicle was repainted in 2015, but not in the original colors and not with the original hood (why the hood change?). In fact, the hood is off a 1985 Seville and differs in trim from the 1980. We’re told the Caddy runs and drives and comes with spare injector pumps (sounds like this car has gone through a few). Like we said, it runs, but the seller is clear in saying there are no guarantees. Diesel anyone?
If I am not mistaken, this was the first American car to cross the $20,000 threshold. That sounds quaint now, but it was a huge deal at the time.
A minor correction for the author: The Olds Diesel was not a modified gas 350. The block is different, the crank is different, the bearings are different. It’s all different. About all that interchanges are some misc parts, like the rocker arms and oil pump. The cost savings was from using the same dimensions and head bolt layout, so existing machine tooling could be used for both gas and diesel. It’s what makes the diesel blocks so desirable for high HP gas builds.
1978 essentially gas blocks. 1979 and beyond DX and D3 block had heavier webs and cross bolted mains. This one would have been built with DX.
Nice to see someone who knows what he’s talking about. There are way too many misconceptions about the Olds diesels. One main thing is that these were meant more for highway use than in city. Short trips are death to a diesel. Leads to things like old moldy fuel, oil gumming from water buildup in the crankcase and many other maladies that affect all ICE engines, only more so on diesels. I’ve had nothing but great service out of the ones I have owned. You take care of them and they take care of you.
My buddy’s father had one of these, sow, oh so very slow on take off, 0-60 in 3 days…… 😄
Thank you !!!
I love learning things from other readers’ comments . . .
Pre-1981 diesels are built on the 350D block, though. While they’re stronger than the Oldsmobile 350 gasser block, it’s not the equal of the far better 350DX block.
Sounds like this is a candidate for a SBC! At least it would keep it in the family.
Would you tell me how you would hook up a small block Chevy to a TH325 or a TH3254L? You might be reading too many magazines.
This would have the original THM325, not the later overdrive, but you’re correct that he’d need an adapter, if there’s even one available, to put any engine with the Chevrolet bellhousing bolt pattern. The THM325s (and the THM425s before that) used the BOP (and Cadillac) bolt pattern.
The diesel used the standard BOP engine bolt pattern. I like the style of this car. If I stumbled across a nice one of these at a good price. I would be tempted to do an engine swap with a 455 Pontiac engine. (Virtually the same outside dimentions) I had a good customer back in Illinois who was always on the road as he was in sales. He bought a Caddy DeVille with the diesel. He put 150,000 miles on that car in no time. He loved the fuel economy, but hated the noise and smell. He never had a reliability issue with the car. But went back to a gas engine the next time around.
I rather put a nice 350, 400, 403 or 455 Oldsmobile gas engine in it. That would be an easy swap that we did so many times back when these worthless diesels were on the road.
This is just one of the reasons GM lost it’s automobile sales lead from back in the 60s. GM built these things but did not support them when times got tough and owners had to fork out so much money to keep them on the road. It was a disgrace that GM placed on their buyers.
its clean and looks to have had an updated motor at some point. seller sounds fed up. easiest way out is put a 350 olds gas engine it and be done. drops right in. we did many back in the day at the olds dealer.
In Seattle there was a Wreaking Yard that would switch the diesel out. I think like a grand or 1500. My brother did it to his cutlass.
The seller couldn’t pay me $3700 to take it off his hands with that engine in it! I had one with the 4-6-8 features and that was junk also!
My gas powered one was a POS, but the diesel is a legendary dog.
I used to pump gas (in the mid 80s) and a guy used to pull in all the time with one that had the diesel swapped out for a gas engine. Every time I’d lift the license plate and see the wide filler tube and “DIESEL ONLY” warning sticker I’d have to pause. That diesel must’ve died within 5 years, max.
I had a 1978 Seville. By far…the worst car I ever owned! The car was on a car carrier 5 times due to breakdowns! All my other cars, (about 20), combined never needed a car carrier! Once I was able to get rid of the Seville, I switched to Lincoln and have never once regretted that decision. But it’s getting harder to find decent Town Cars. I have two now, (one winter, one summer). My black on black Town Car has received more compliments that all the others combined!
Maybe a new hood as the old one was damaged in the fire?
The GM Diesel’s were total junk !! My brother purchased one it was always broken down but I warned him 😞😞😞
Too bad it’s the diesel. The optional 6.0 was the ticket on these, and the 1980 was the one year without the hated 8-6-4 nonsense, though that was easily defeated by simply unplugging a wire.
Though not mentioned in the listing nor in the BF write-up, this Seville appears to wear the uplevel Eleganté trim.
GLWTS.
In the era I remember some guy had a new Caddy with either the diesel or their cylinder management crap. It was constantly in the dealership. They finally refused to fix under warranty. In the beauty of “ don’t get pissed off get even “, this fine Gentleman ( my hero ), rented the vacant lot next to the Caddy Dealer, hired a big crane, invited all the LA media, TV, Radio, print etc etc. then had a small press conference, hoisted the car up the height of the big crane and dropped it, set so the cameras would have the dealers sign in all photos!!! Haha.
From what I recall back in the day, cylinder head bolts were one of the weak links on the 350 diesel. It was common for them to either stretch, work loose, or snap and thus blow the cylinder head gaskets.
When they were running, they delivered 25+ miles per gallon which was phenomenal. However, in typical GM fashion, the design was half-assed (IMO) as the bean counters and marketing out-weighed the engineering dept…much like what has happened to Mercedes-Benz in the last several decades.
Had one of these. Black and silver though. Worst car I ever had. It was in the shop more than I could drive it. They never could get the diesel running right. Lost my butt to get rid of it
Just like Pontiac ( aztek,70’s grand-am) and Harley Davidson ( AMF, Livewire, $40,000 Garbage Wagon) Cadillac has had it’s failures,This is One! Two was the 4-6-8 Engines! GM should have kept Pontiac, at least they made vehicles for the lower class people like myself and not $100,000 pick-up trucks with 6 cylinder Firecrackers with Turbos! Really? Heat is the Nemisis of any engine and don’t ignore the 10 speed can’t find a gear transmission!
Love a diesel Cadillac. Next owner will have to know what they are doing. Those engines do well if you know how to service them.