1978 Oldsmobile Delta 88 Diesel: In Defense of the Olds 350 Diesel V8

My Grand Dad always had a beater, for everyday driving, and a good car, which he bought new and brought out only on special occasions. Once, he said he’d buy a new car when he retired and give his current garage queen, a 1966 Chrysler sedan, to my Dad. In 1977, Grand Dad did retire, and Dad held him to his word.  To replace the Chrysler, he headed down to Carter Chevrolet-Olds and placed an order for what is oft regarded today as one of General Motors’ biggest blunders: a 1978 Oldsmobile Delta 88 with the then-new 350 CID LF9 V8 diesel engine.

The Delta 88 4-door sedan was the most popular 1978 Olds to be ordered with the LF9 diesel. Much like the base-model 1966 Chrysler, the 1978 Oldsmobile Delta 88 was advertised as more car for not much more money than “lesser” automobiles. Undoubtedly this appealed to Grand Dad’s innate frugality, as it still allowed him to have an upscale, but not ostentatious, full-size automobile.

Aside from the special engine, Grand Dad had ordered his Olds equipped in pretty much the same way as his Chrysler. Both were finished in metallic maroon, his favorite color. Inside, both had an AM radio but no other optional power or comfort accessories. The Olds came with a rear window defroster, which I believe was part of the upgrade to the larger alternator that was mandatory with the diesel.

At the time, rising gas prices were certainly of concern, as were the Rube Goldberg-style emissions controls that strangled the gasoline engines of the day.  On paper, the diesel engine looked to be a godsend:  Advertised fuel economy for the LF9 was head-and-shoulders above the other engine choices, even with a three-speed, non-lockup automatic transmission.  Today, the performance figures of the LF9 (rated at 120 hp) would be considered laughable, but at the time they bested the contemporary European diesels on the market.

(Image source: Popular Mechanics, Sept. 1978, via Google Books)

Early buyers were initially very pleased with their purchase.  A survey of 1,000 Olds diesel buyers, published by Popular Mechanics in September 1978, reported that 97.4% said they would buy another Olds diesel!  Also, owners were actually getting fuel mileage that came close to the EPA numbers.  Then came the inevitable breakdowns.  The engine quickly garnered a bad reputation as a lemon, and eventually became the poster child for why America ultimately rejected diesel passenger vehicles.  So what went wrong?


It’s a common misconception that the Oldsmobile LF9 diesel was simply a 350 small block hastily jerry-rigged to run on diesel fuel. This misconception came about because the locations of cylinder-head bolts and some other critical dimensions were identical to the gas-fed small block so that both blocks could be machined on the same equipment during manufacture.

(Image source: http://www.robertpowersmotorsports.com)

The LF9 engine block was a unique casting with extra reinforcement; the entire reciprocating assembly also was unique, with all its components heavy-duty. The larger, 3-inch-diameter main bearing journals it used in place of the normal 2.5″ journals were the same as in a big block; however, its commonalities with the garden-variety small block made it possible to bolt gasoline-engine heads onto the LF9 block, and (along with other modifications) convert it into a gas engine.

While some industrious engine builders have overcome the technical hurdles to accomplish this, the rework costs make it impractical for all but maximum-performance applications. A converted LF9 can be generously over-bored and built for higher power than a regular small block without grenading in racing applications.

Diesels are very sensitive to water contamination in the fuel system. Diesel fuel contaminated with water results in much higher-than-normal combustion pressure–high enough to blow head gaskets and snap head bolts. It is true that the LF9 head bolts were under-designed, especially on those built prior to MY 1981. The problem was exacerbated by improperly trained dealership mechanics who had to service this engine. When changing a blown head gasket, they typically would just replace any snapped head bolts, just as they would on a gas-powered GM V8. However, the diesel used “torque-to-yield” head bolts that required the entire set to be replaced when changing a head gasket. Otherwise, more head bolts were bound to fail, and the vehicle would soon be back in the shop in need of another head gasket.

Unfortunately, as a cost-cutting measure GM did not outfit their diesel cars with a proper water-separating fuel filter. A “water in fuel” (WIF) sensor was installed in the fuel tank, as well as a warning light on the dashboard. In the Delta 88 the WIF lamp would have been located in the panel above the HVAC controls. The WIF warning lamp was GM’s work-around for the lack of a proper filter. Owners ignored this warning light at their (and their vehicles’) peril. Compounding the problem, some well-meaning owners simply added “dry gas” (alcohol) to the fuel tank when the WIF light came on instead of having the fuel tank drained. Alcohol is incompatible with diesel fuel-injection systems and ruins the seals in the injection pump.

In my memory, the only times Grand Dad actually drove his Olds were on the way to my brother’s birthday party every August, to his annual summer visit to his brother in Maine, and (begrudgingly) during a short stint one winter, when his beater needed repairs. I remember him keeping the block heater plugged in to ensure there wouldn’t be any starting problems in the cold weather. It was the only time that block heater was used.

I also recall Grand Dad briefly putting the Olds up for sale. He had somehow convinced himself that he wanted a Thunderbird Turbo Coupe. It wasn’t for sale very long, either because the only interested parties were tire-kickers that wanted to lowball him on price, or because after my Dad informed him that the turbo-bird drank premium gas, he didn’t want one after all.

After Grand Dad passed away, in 1989, my Dad inherited the Olds. It became a regular summer driver in our household, but remained stored safely away from winter weather and the ensuing road salt. I’ve personally logged a fair bit of time in the driver’s seat. In 1999, the year I graduated from school and started my full-time career, I borrowed the Olds for most of the driving season. Defying the odds (considering its poor reputation and the over 130,000 miles on the odometer), the original power plant still resides underhood in relatively original condition (including head gaskets!)  That this car is still with us today, and hasn’t exhibited most of the usual maladies these engines were known for, can be credited to a combination of good maintenance practices and good fortune.

Early production cars didn’t even get the water-in-fuel sensor, so a recall was issued to retrofit it. Some time after receiving his new car, Grand Dad was notified of the recall notice. When he went to the dealer to have the WIF sensor recall applied, he was told that it was no longer being performed, and instead they would install a fuel filter. In reality, they were probably being lazy; the recall procedure involved draining and removing the fuel tank to install the sensor and disassembling a fair amount of the dashboard to install the WIF warning lamp.

What the shop actually installed–a big blue canister visible in the engine compartment–is the kind of  large diesel-fuel filter  typically found on commercial trucks. There is a petcock at the bottom for periodically draining off any water it has collected. I attribute the uncharacteristic longevity of our Olds to this filter as much as anything else.

Another common problem with these engines involved their propensity to eat camshafts and crankshafts. In both cases, that could be avoided by using the correct diesel-rated crankcase oil and changing it promptly at the prescribed 3,000 mile intervals (or preferably sooner). The first-gen used a flat tappet camshaft, but the valve spring pressures were considerably higher than would be typical for stock gasoline engines. Additionally, the crankshaft bearing material was designed for use with diesel-rated oil only. If you slacked off on the oil change interval, and trusted your car to whatever oil the local monkey-lube installed, valve train and/or bearing failure was inevitable. Ultimately, GM made the engine more tolerant of typical owners’ maintenance habits: The second-gen LF9 diesels received roller cams and revised bearings, which extended their service interval to 5,000 miles and permitted the use of non-diesel-rated oil.

This particular car has enjoyed every-2,000-miles oil changes with diesel-rated 30W oil since it was new. The rockers wore out and needed replacement once, but the rest of the valve train is original. Naturally, there have been other repairs over the years. For instance, one of the cylinder heads developed an external crack in the water jacket and my dad, who figured he had nothing to lose, simply welded the crack shut, with the head still on the car. It worked!

Another time, one of the plastic T-fittings on the fuel return lines cracked. Diesel fuel spraying on the exhaust manifold resulted in billowing white smoke from under the hood; fortunately, it didn’t ignite. The Stanadyne fuel injection pump has required two overhauls, and the injectors one. Presently, the car has a small fuel-system leak somewhere, probably just a cracked rubber fuel line, that causes the pump to lose prime after sitting. It requires lots of cranking to re-prime the system before the engine clatters to life.

In typical fashion, GM rushed the LF9 engine to market with a combination of underdevelopment, beancounterism, and lack of dealership-mechanic training. After weathering a barrage of bad press from reviewers and purchasers during the engine’s first few years, they cancelled production despite finally having gotten most of the bugs worked out. Of course, by the mid-80s, gas prices had fallen, there were government threats to more closely regulate diesel passenger-car emissions and the LF9 had developed a bad and seemingly unshakable reputation. It had basically become unsalable.

If only GM had installed a proper fuel filter, made some of the second-gen improvements up front, and taken the time to properly train their dealership mechanics in servicing the engine. No, they’re not for everybody–the LF9 was still an old-school diesel with no turbo to give it more power, nor electronic fuel injection to quiet it down–both of which are ubiquitous on moderns diesels–but still, I think diesels could have had a future in full-size American sedans.  There was already an established niche market for them among European-car buyers, who were turned off only by the lack of dealer support for their imports.

Based partly on our own favorable experience with Grand Dad’s Olds, my family got hooked on the economy and low maintenance costs of diesel power.  We’ve since owned several VW diesels, GM 6.2-liter diesels, a Cummins-powered Dodge and a Chevy Duramax.  If diesel power had continued to be an option in domestic full-size sedans, this list probably would be even longer.

(Most pictures for this article not taken by my Dad were sourced from oldcarbrochures.com)

31 Replies to “1978 Oldsmobile Delta 88 Diesel: In Defense of the Olds 350 Diesel V8”

  1. EquipmentJunkie

    I knew of lots of people who owned 5.7 GM diesels. It seemed like those who were mechanically inclined and were fastidious about maintenance had good luck with them. The second generation engines were especially good as long as expectations were properly managed. I even had a co-worker that resurrected his Dad’s ’82 Olds 88 as a daily driver a few years ago. The inability to find replacement injector nozzles for it eventually forced its retirement.

    I once heard a quote about either the 5.7- or 6.2-liter GM diesels that always made me chuckle:
    “Driving a 5.7 (or 6.2) GM diesel is like walking around with an un-pinned grenade in your pocket…you know it’s going to really hurt, but you don’t know when!”

    • EquipmentJunkie

      Mike Batch Kirouac (AKA BigOldChryslers), I forgot to compliment you on your fine article. I learned a lot. I’ve been a loyal supporter of Dr. Rudolph Diesel’s offspring over the years. I had very little specific knowledge of the 5.7 GM diesels since I was under 10 when they were first introduced. However, I can still identify the house where my father and I spied our very first Olds Delta 88 diesel.

  2. Dave

    A neighbor was a manager at Stanadyne in Windsor CT where they made the fuel injection pumps. He bought a new diesel Chevy Caprice Classic sedan in the early 1980s. I recall he bought it to tow a small camper too! Although I think he discovered quickly that was not a great idea.

  3. dejal

    “If only GM had installed a proper fuel filter, made some of the second-gen improvements up front, and taken the time to properly train their dealership mechanics in servicing the engine.”

    If my aunt had a package, she’d be my uncle.

    Remember this is GM you are talking about. The GM from way back when. I’d like to think the “New” GM would have done what you suggest, but even now it’s not a lock they would. The fact that the mechanics didn’t work for GM still gives the impression that it was GMs fault if you trusted the mechanic. Especially dealer mechanics as they represented the GM technical expertise even if not GM employees. Remember Mr. Goodwrench?

    In that era they did a similar thing to the Fiero. Worked the bugs out, made a lot of improvements then canceled it.

  4. rnc

    I don’t remember my dad’s 83 98′ Diesel having a lot of problems and he actually kept for a long while. It was however his last GM car. The car before that was his first Caddy, I was too young to remember what was wrong with it, but I hated riding in it, you could just feel anger and not realize that it wasn’t directed at you (like army Col. anger). Anyways the dealer took back the Caddy and gave him the 98′ in return. Everything after that was Towncars and Navigators.

  5. CJinSD

    Those Popular Mechanics owner surveys from forty years ago are interesting reading. Typical Detroit cars had very unhappy owners at the time. The manufacturers were having a very hard time meeting emissions standards while reducing fuel consumption. The result was cars that stumbled when you tried to accelerate, had hot starting or cold staring issues, and that ran on or ‘dieseled’ when shut off. On top of that, efforts to reduce NOx emissions and tall gearing chosen for the EPA dyno test meant that real world fuel economy was disappointing too. The result was that it was pretty normal for over 30% of the buyers of some popular cars to immediately regret their decision and say so in the PM surveys. The Oldsmobile Diesel was the domestic exception. People were so happy with the running qualities and efficiency that they didn’t complain about fit and finish or pretty much anything else. They loved their new cars.

    Then the other shoe fell. GM had already unleashed the 2300/Durabuilt 140 on their customers at this point. It probably wouldn’t have been a bad idea for Olds diesel buyers to take a wait and see approach. This defense sounds more like an act of apologism. If you didn’t think engines that need their engineering completed by owners in the field were a good thing before, you probably don’t have a higher opinion of the 350 diesel now than before reading this piece.

    One of my good friends has a Jeep, a Porsche, and a mechanical engineering degree. He’ll tell you that cars aren’t bad, it’s the owners who ruin them. He also spends about two weekends a month with one of his cars taken apart in his garage. Even doing all his own labor effectively, he spends a fortune on parts and special tools. I can’t tell if he realizes that he has a hobby rather than a rebuttal of my arguments for buying a Toyota product. His teenage son’s 2018 WRX automatic needed new VVT actuators and an ECU at 13,000 miles. Fortunately for him, he’d refused the reflash that Subaru dealers recommend when you buy a WRX or STI to void your warranty. He still needed to produce proof of every service before they honored the warranty. Subaru may finally cure him of crummy cars. Seeing the car fail so early and the dealer try every avenue of escape from responsibility for what is clearly a low quality product may well convince him to buy a good car next time. If that happens, he’ll be just as mystified by people who defend shoddy products as I am.

      • CJinSD

        Porsche money might buy you an LC500 or a Land Cruiser, both of which are better than anything Porsche offers in their market spaces.

        • arbuckle

          Yes, Toyota does make a better off-road SUV and a better GT coupe than Porsche. Check-and-mate, Mr. San Diego.

          However, as I’m sure you are aware, Porsche has built many thing throughout its history that are not off-road SUVs or Grand Touring cars.

          • CJinSD

            History is for books. What does Porsche make today that you’d go into debt for? They’ve got nothing I’d bother putting in my rotation for free. Automatic turbos are for automatons and video game playing onanists.

        • dejal

          People have a lot more tolerance for toys.

          If you need a “I have to get to work. I have to get to XXXX. and I can’t be screwing underhood on cars all the time”, I’d take the Toyota. Better odds. For a play thing? Nope.

          • Carmine

            There must be so many unemployed people that don’t own Toyotas……..

            How does anyone else get to work?

            No wonder the economy is struggling……employees can’t get to work because of all those insanely unreliable non Toyota cars they own.

            We really need to change to Toyota Ambulances in this country, no one would ever die…….because they would all get to the hospital every time.

          • dejal

            I can’t directly answer Carmine below.

            Did you want me to say “Honda, Toyota, Chevy, Chrysler, Ford, Lincoln Mercury, Nissan, Hyundai, Kia, Buick, etc….”? Maybe “Main stream car sold in bulk” would be better?

            I don’t even own a Toyota. I just said Toyota because that was the brand mentioned upstream from me.

            May I suggest

            Substitute Toyota for Heineken.
            You will forever look and sound like “Frank” from Blue Velvet in my mind from now on.

          • Tom Klockau Post author

            I think he was responding more to the permanently cranky guy. Sometimes when you reply to a comment, they pop up in a different spot. 🙂

      • Carmine

        The amazing thing really is that in the all the history of automobiles, there has never been a recorded incident of a Toyota breaking down?

        You know their dealers don’t even employ mechanics or even carry spare parts??

        Never had a recall or anything…..

        Its amazing, they just keep running, they don’t even need gas or oil……


        • arbuckle

          “History is for books.”

          Classic and late model cars are a thing (just ask the guy running this website). You can’t simply handwave them away as you lug the goalposts down the field. The Macan being a trashcan doesn’t cause every 964 to turn to dust.

          And what does your friend own? Is he really spending two weekends a month DIYing a 2015 Cayenne?

          • CJinSD

            Most of my 911 time has been in 964s. That being said, they only became good when the 996 arrived. They’re damned old now too. So old that they aren’t viable transportation, which is what matters to me. There are all sorts of cars that I’ve driven or wanted to that were made before people could be elected in the US as admitted socialists. I’m concerned about what is available if I need a new car. Porsche has nothing. I’d tolerate their abysmal quality and east German engineering if they’d give me a naturally aspirated engine connected to a stick for the high five figure price I can stretch to. That ship has sailed.. I watched them descend into being a neo-classic brand with a good relationship with Michelin. At least that could be justified by their lame customer base. What they’re doing now goes beyond embarrassment. It isn’t like fucking a fat girl in the dark. Driving a new Porsche is about as desirable as fucking a fat boy in a dress. You go ahead though.

          • Tom Klockau Post author

            Well golly, arbuckle, don’t you remember all those kids who had posters of a beige beigemist Camry in their rooms? It was a real hot ticket. Oh wait, no, that was the 911, Corvette and Countach. My mistake… 🙂

          • CJinSD

            Says the guy who writes paeans about the cars that lobbed floaters across the plate for Toyota to knock out of the park with the Camry. If a Camry is boring, what is an Oldsmobile? Excuse me. What was an Oldsmobile?

          • Carmine

            I’m actually surprised he lowered the mighty LC500( I had to google it to remember what it was-the Lexus Camaro…..they sold like 4 last year) to compare it to the toilet bug that is the Porsche 911.

            Surely someone looking at a 911 would probably be happy with a 2003 Solara or something, save the mighty LC500 for comparisons with worthy vehicles, like a Tardis, the Millennium Falcon or supersonic hovercrafts…..

          • Carmine

            What angle are you going for here CJinSD?

            Baruth Light but without the talent or humor?

            Try something else, no one is going oohhhh and ahhhh……

          • Tom Klockau Post author

            Carmine, I always find it interesting how much hysterical commenting can result from a car that hasn’t been built in nearly forty years. “It was him, Officer! He’s the one that ruined everything! Him and his friends and that stupid dog!”

          • Arbuckle

            “if they’d give me a naturally aspirated engine connected to a stick for the high five figure price I can stretch to”

            You could buy a naturally-aspirated, stick-shift, RWD Porsche for under $100K as late as 2016. That’s hardly classic car age.

            But anyway, I have no major affinity for Porsche, whether modern or classic. I’ll just point out that you recommended your Porsche owning friend to buy “a Toyota product” and not some hardcore stick-shift sports car.

        • yamahog

          What’s more amazing is that Toyota seems to be the only company who considers the ownership experience of the second, third, …, and last titled owner.

          Toyota redesigns their cars about half as often as everyone else, they have relatively few options, and their safety / production technology is usually as good as it gets but they seem last-to-market with almost everything else (the 2018 Camry is getting apple carplay this year for example).

          But in my neck of the woods, the only vehicles that last longer than 15 years are GM+Ford trucks and good Hondas and most Toyotas. It’d be great if another manufacturer were willing to compete with Toyota on quality but they’d all rather stuff their vehicles with infotainment, and tie the company’s bottom line to the willingness for banks to finance $3k sport-in-name-only packages that really offer bigger wheels and really special trim.

          • Arbuckle

            I have no real quarrel with Toyotas. My issue is when people act like a Toyota is the proper substitute for everything. Not everyone has 2 decade longevity and a happy final owner as the number one item on their shopping list.
            From your prior comments here, you like high-powered motorcycles. Someone telling you to get a RAV4 instead of an R1 would just be goofy.

          • safe as milk

            “the only vehicles that last longer than 15 years are GM+Ford trucks and good Hondas and most Toyotas.”

            the auto industry has clearly decided that only the first 10 years of ownership count. the pressure to meet cafe mpg numbers and offer awd has pushed them to now all use ridiculously complicated and expensive automatic transmissions which are sealed with “lifetime” fluid. the trans blows at 120k miles and you junk the car. end of story.

  6. David Schaffnit

    We had several Olds 88 with the diesel engines when I worked in Odessa, Tx. The regional mechanic that worked out of out shop kept a rebuilt engine with appropriate transmission ready to install and when one died it was a half day to get the car back on the road. One problem was the fresh air snorkel. The dealers always hooked it up but one trip through a low water crossing was all it took, with the snorkel in place to kill an engine.

  7. safe as milk

    great article on a fascinating engine. i really like the details about what actually did fail and why. much better than the usual, ” i had no serious problems with mine.”

    there’s and aftermarket kit that allows mechanics to rebore the heads to take beefier studs for these engines. the car wizard on the tube is putting one in his ’69 caddy broughm, believe it or not.

    • Carmine

      I saw that video, it confirmed that he was an idiot, I only has suspicions earlier…….

      Though I guess doing something smart is not the way to get YouTube views I’ve learned.

  8. Andreas Winter

    I still drive an 1978 Olds Diesel. The engine was replaced with a DX block. I found out when I replaced the lifters. Shortly after that I had to open it up again because 2 head bolts snapped. I replaced all of them with ARP head bolts and I didn’t have problems for the last 7 years.


Leave a Reply

Your email address will not be published.

This site uses Akismet to reduce spam. Learn how your comment data is processed.