Oldsmobile’s V8 Diesel Was A Good Idea Gone Horribly Wrong

Most of you reading this will be familiar with the gas crisis of the 1970s. The first Gas Crisis hit in 1973, immediately following the Organization of Arab Petroleum Exporting Countries’ oil embargo, which went into effect on October 17th of the same year. It shook the American automotive market to its core, as most cars on the road at the time were equipped with gigantic, fuel-guzzling V8s that were lucky to achieve more than 10 mpg on the combined cycle.

The second Gas Crisis landed on American shores in 1978, but this time, General Motors had an ace up their sleeve, or so they thought. At the time, diesel was much cheaper than regular gas, prompting the Detroit Giant to develop a diesel engine for use in passenger cars. The idea was great on paper, and promised much better fuel economy than regular gasoline-powered engines without sacrificing the smoothness of a V8. However, the difference in outcomes between a plan in theory and in action can sometimes be drastic.

A Good Idea, Badly Executed

Oldsmobile Diesel Engine Program Facts

• Production began in 1978
• Initially offered as a 350-CID V8, a V6 version was offered in 1979 and again in 1982
• Largely based on the Oldsmobile 350-CID gasoline engine
• Plagued by severe problems throughout its early life

Oldsmobile’s response to the second-coming of the Gas Crisis was a swift one. While other automakers were trying more and more to push smaller, more economical cars, Oldsmobile was busy trying to save the big-bodied luxury cars Americans were accustomed to. Because cars like the 1977 Oldsmobile Ninety-Eight and the 1977 Lincoln Town Car only managed roughly nine mpg around town, and with gas being so expensive all of a sudden, the American land yacht was in serious trouble.

Back in the late 1970s, diesel was much cheaper than gasoline, chiefly due to smaller demand. In order to capitalize on diesel’s lower price during the Gas Crisis, Oldsmobile quickly retrofitted their 350-CID V8 to run on diesel fuel. For context, a gallon of gasoline costs roughly $0.86, whereas a gallon of diesel was priced at $0.56. When we factor inflation into these prices, gasoline costs $3.74 in today’s money, while diesel costs $2.43. In essence, it was a larger price gap than you’d think.

During the engineering phase of the project, a few key issues were overlooked in order to reduce production costs. These oversights ended up quickly becoming the bane of Oldmobile’s diesel plans. After just a few short years, the diesel engine would end up tarnishing the American public’s opinion of diesel-powered passenger cars for decades to come, all because some GM execs wanted to pinch a few pennies.

The Oldsmobile Diesel Engines Saw Widespread Use

The most commonly-used iteration of the Oldsmobile diesel engine was the 350-CID V8. As we touched on just a moment ago, it was the first version to be introduced. Immediately, General Motors began utilizing the engine in several of its subsidiaries, including Pontiac, Chevrolet, Buick, Checker, and even Cadillac. GMC also used the mill in their Caballero and C1500 pickups, although only in an automatic, RWD configuration.

Below, we’ll take a look at each version of the diesel engine and their basic specs. Average fuel economies used were based on the most fuel-efficient model each respective engine was featured in:

The 261-CID V8, based on the 350 V8, was introduced in 1979. It was only featured in the Oldsmobile Cutlass Salon and Oldsmobile Cutlass Supreme/Calais, and after just a single model year, it got the ax due to awful sales figures. After a disastrous first couple of years, Oldsmobile developed a new line of diesel V6 engines to be sold in tandem with the 350 CID V8. The V6 lineup saw less widespread use than the V8. In total, 37 General Motors nameplates used some form of Oldsmobile’s diesel engine throughout its seven-year tenure.

How It All Went Wrong

There are a few answers to that question, all of which involve how the Olds diesel engine was engineered. At its base, the original 350 CID diesel V8 was largely based on Oldsmobile’s existing 350 CID gasoline V8. Many of you will know that gas and diesel motors contain a few fundamental and important differences, right down to things like cylinder head design and strength. Gasoline and diesel fuels are also quite different in how they burn. The amount of compression needed to create proper combustion within a cylinder head is radically different.

The most glaring problem the diesel engine faced was cylinder head bolt failure. At the time, gasoline engines typically boasted a compression ratio of around 8:5.1. However, diesel engines require quite a lot more compression in order for the diesel fuel/air mixture to properly combust. Rather than make integral changes to the gas engine’s cylinder head or head bolts in order to handle this massive increase in compression, which sat at 22:5.1 for the diesel variant, they did nothing. This caused catastrophic engine failures in as little as 30,000 miles in some cases.

Another major issue with the diesel was its lack of a water separator. In diesel engines, a water separator is needed in order to filter out water that may be present in low-quality fuel, or due to condensation building up in a vehicle’s fuel tank. Because diesel fuel was much lower-quality back in the late 1970s, water intrusion was a major issue that plagued these motors. Reportedly, many diesel owners resorted to pouring anhydrous alcohol into their fuel tanks to dissolve any water, but the chemical ended up eating through the rubber seals in the fuel system.

Finally, to top off the diesel’s pair of catastrophic issues, the early motors were also supplied with an inferior timing belt. It was made of rubber and tended to stretch to intolerable limits. This led to some motors experiencing something called “timing jump”, where an engine’s timing belt or chain moves out of position, resulting in the engine’s valvetrain being out of sync. This can result in premature engine wear and even failure if not promptly fixed.

By 1981, Oldsmobile had, largely, fixed all the issues laid out above. However, because of how awful the first three years of service were, the Oldsmobile diesel program had suffered such a negative dip in reputation that it never recovered. In fact, the American consumer was so turned off by the failings of the Oldsmobile diesel program that sentiment towards diesel-powered passenger cars was tarnished for quite a while.

Why Europe Loved Diesel Cars So Much

In a stark contrast to Americans’ mistrust of diesel-powered passenger cars, Europe readily adopted diesel cars for use in everyday life. One of the largest reasons for this is due to differences in tax on diesel fuel. In Europe, diesel has historically been much cheaper than gasoline. While this has been seen in the States as well, Europe’s diesel prices have spent a much longer time being cheaper than gasoline.

Diesel cars were also subject to tax breaks and buyer incentives in Europe. Programs such as these were much more common in the past, although incentives still exist for companies who are interested in purchasing a fleet of diesel-powered cars for use as company vehicles. However, these programs are, reportedly, selective, and mainly apply to large corporations making big purchases.

As time wears on and the push for electric vehicles becomes more and more forceful – especially in Europe – the diesel car has lost much of its popularity as the programs, incentives, and diesel fuel tax breaks begin to wane. It seems the diesel car may not exist, or exist on a niche level, in the not-so-distant future. As bad as it was, we have to thank Oldsmobile for pioneering the use of diesel fuel in cars for those of us in the US. As we said before, it was a great idea, but horribly executed.

Sources:
General Motors, Chevrolet, GMC, Buick, Cadillac,
NPR.org