Automotive History: Oldsmobile 5.7L Diesel V8 – GM’s Deadly Sin #34 – Premature Injeculation

In the late ’50s, GM’s Detroit Diesel Division’s “Million Miler” -71 diesel engine was so superior to the competition, resulting in such market dominance that GM was forced by an FTC consent decree to sell it to its competitors.

In the early ’80s, GM’s Oldsmobile Division’s passenger car diesel engines turned out to be such a disaster, the FTC had to step in and broker a massive compensation deal on behalf of millions of its angry buyers.

The 1950s were GM’s golden decade; the 1980s its living hell. And the Olds diesel sprayed plenty of fuel on those flames.

The 1973-1974 energy crisis shook the foundations of The Big Three’s business proposition, which was always tilted heavily to large cars. Detroit built small cars reluctantly, because the fat profit margins they had on big cars just weren’t there, if any at all. And realistically, most Americans weren’t going to be happy with the Pintos and Vegas they bought in the depths of 1974 once the OPEC oil taps were turned on again.

In response, in 1975 Congress passed the Energy Policy and Conservation Act, which resulted in CAFE (Corporate Average Fuel Economy), set to take effect in 1978. The initial 1978 target number was 18mpg, tightening up substantially to 27.5mpg in 1985. The energy crisis was becoming an existential crisis for GM.

The first order of business was to start an across the board downscale program, which would become to be the biggest corporate investment program to date. Every line was to be completely new, starting with the large B-C Body cars in 1977. Reduced weight and improved aerodynamics allowed the return of six cylinder engines and smaller V8s, with significantly improved EPA mileage numbers.

In the case of this 1977 Chevrolet, the six cylinder version’s EPA rating was a 33% improvement over a ’76 with the 350 V8, and the ’77 305 V8 version was rated 20% better. A good start, but GM knew that it would have to keep improving those numbers in coming years. That led to various programs to further reduce weight and improve aerodynamics with these B-C Bodies, as well as improved drive line efficiencies. One of those programs resulted in the 1981 Cadillac V8-6-4 engine, with cylinder deactivation. It turned out to be highly problematic, due mostly to its electronic control module being underdeveloped and unreliable.

Other programs included the expanded use of the Buick V6, and Chevrolet developing a 90 degree V6 derivative from its small block V8. And there were lighter and further downsized gas V8s, like the Pontiac 301 and 265, the Chevy 267, and the Olds 307.

But there was another avenue yet to explore: the diesel. And there were a number of compelling reasons.

GM had been keenly aware of the rapidly growing success of Mercedes, and that an increasing percentage of them were diesels. The fact that upscale buyers would gladly pay 2-3 times as much for a slow, sometimes smelly and sooty diesel compared to a big GM sedan must have been painful. A diesel Mercedes was the hot new status item for those that couldn’t quite swing a 450SE or SL.

Peugeot’s 504 diesel was hot too. Like Mercedes, Peugeot had a half century of experience in the field. And who the ad referring to?

And in 1976, VW jumped into the diesel market in a big way. The Golf/Rabbit’s diesel was a direct development (“conversion”) of its gas engine, and showed that it was not necessary to start from scratch in building a successful diesel engine. As such, it offers a counterpoint to the Olds diesel, both being converted gas engines. It resulted in an extremely economical yet surprisingly agile car, changing the image of a modern diesel. And it turned out to very durable. The Europeans appeared to be showing the way forward.

Rudolf Diesel’s namesake engine had a couple of very compelling qualities at the time. It needed no emission control systems, as it inherently had lower outputs of HC and CO, and NoX standards were still very generous at the time.  Gas engine emission systems were becoming more complex and expensive with each tightening of the EPA standards.

It intrinsically was more efficient than a gas engine, roughly 25-40% more so for a given displacement. In addition to the obvious benefits, this also resulted in significantly longer range between fill ups, another advantage at a time when memories of gas station waiting lines were still fresh.

And diesel fuel was still consistently cheaper than gasoline, as a result of the imbalance of demand, taxes, and as well as other factors.

Maintenance was potentially reduced, as there was no ignition system, emission system, carburetor, or complex electronic fuel injection system. Oil changes did require shorter intervals (typically 3,000 miles), and the oil capacity was usually greater. But the appeal of the diesel’s intrinsic simplicity was compelling.

So in 1975, Oldsmobile, long known as GM’s “experimental division”, began the development of a diesel engine. Before we go any further, let’s quickly address a common refrain: why didn’t GM give the job to Detroit Diesel, which had been building diesels since 1933?

For several good reasons. To start with, Detroit Diesel’s two stroke engines, initially developed by Charles Kettering at GM Labs in very large format,  operated quite differently, with its necessary expensive blower. They were also extremely noisy, due to being direct injection as well as being two-stroke engines, which made them sound as if they were running at twice their actual engine speed. All passenger car engines were then still indirect injection, as the violent percussion of direct injection had not yet been tamed.

I’ve seen the smallest of the DD’s, the 4-53, swapped into pickups, like this one in an International, but it’s not done for practical purposes. They are very heavy, loud and rough, and the two stroke design does not like lots of low rpm use. It was absolutely not suitable for passenger car use.

A more obvious choice might have been the GMC Truck division, which undertook a gas to diesel conversion of its 60 degree V6 engine, which first appeared in 1960. In 1964, the Toroflow diesel appeared, which used a strengthened version of the gas V6 block and internal components and of course a new cylinder head. It’s possible that the V6 was designed in the first place with an eye to an eventual diesel version. Regardless, the Toroflow, intended as a more affordable diesel for medium duty trucks and buses, ended up with a fairly mediocre reputation. Its power output was modest, and it just wasn’t quite up to the abuse it got over the long haul. Not a total failure or disaster, but certainly not a memorable engine family.

In any case, the Toroflow’s direct injection “toroidal flow” cylinder head design also was not applicable to passenger car use. Direct injection diesels were not adapted to passenger car engines until the end of the 1980s. Cylinder head/precombustion chamber design was really the key element to passenger car diesels then, other than making sure the engine was robust.

So the job fell to the Olds Engineers, who first started on it in 1975, according to one source. And the Olds 350 (5.7L) V8 engine was the starting point. Why? Why not? There’s actually no good argument for not starting with a well designed gas engine and modifying it to be a diesel. As a matter of fact, the legendary Mercedes OM621/615/616/617 SOHC four and five cylinder diesels built from 1955 until 1991 were very much based on their gas engine counterparts. I suppose more correctly, one might say they were developed simultaneously with the same architecture and some shared parts. The point is, successful diesel engines do not need to be designed from scratch or unique.

In a R&T article, Olds engineer R. James Benner is quoted as saying “there are no textbooks or papers that explain how to build a diesel”. Really? Maybe hire an experienced diesel engineering firm like Ricardo or Porsche? Or better yet, how about taking advantage of the deep diesel experience at affiliate Isuzu, of which GM owned 34% since 1972?

Isuzu had been building its compact precombustion chamber C-Series engines since 1959. A version of that venerable engine is still clattering away today in this 1982 Isuzu I-Mark diesel that I’ve been following for ten years. It just won’t die.

Let’s see: one version of the Isuzu C220 2.2 L four made 73 hp; if they had just doubled that up into a V8 it would have had 4.4 L and made some 145 hp, or 25-40 more than the Olds 5.7. And I’d still be shooting numerous legendary Olds Diesels clattering away hereabouts. Just how hard would that have been? I’m sure Isuzu would have been thrilled at the prospect. But the NIH (Not Invented Here) syndrome was extremely powerful at GM, a curiously deadly strain at that. Meanwhile, I’ve yet to find a genuine Olds diesel on the streets here in ten years, despite millions having been made.

Ironically, after somewhat mixed results with its later 6.2 and 6.5 diesel light truck V8s, GM finally did turn to Isuzu for the Duramax V8. And it’s compiled a generally excellent reputation over the years, certainly better than the Ford PowerStroke. Oh well.

On to the actual Olds diesel:

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