General Motors First Diesel

oldsmobile diesel


Sometimes automotive companies make mistakes and the story of General Motor’s diesel V8 highlights one of the worst. The time was the mid-1970s and meeting the new American emissions regulations was causing many issues for car manufacturers. The solution, at least to some executives at General Motors, was to rush a diesel engine to the marketplace. On paper this worked because diesels were not subject to the same emissions requirements as gasoline engines. Besides Peugeot and Mercedes had both been successfully selling diesels in the U.S. Though the new diesel engines were destined for all GM’s car divisions, the design responsibility fell to GM’s Oldsmobile group. Working at a frantic pace, the first Oldsmobile diesels hit the lots in 1978. Unfortunately, there were problems.

To begin with Oldsmobile powertrain engineers based the design on the division’s famous 350-cubic-inch V8. It is an urban legend that GM engineers simply slapped new diesel heads on the existing 350 block and did little else. This was not the case. The existing block design was reinforced substantially and was built of a sturdier cast-iron alloy. The trouble came from the heads and the diesel fuel system. In particular, the head bolts.

Diesel engines operate using a compression-ignition scheme. The ideal gas laws tell us that as the volume of a gas is compressed, its temperature goes up, and, in the case of a diesel engine, it’s compressed until the diesel fuel in the combustion chamber explodes. Designing for this leads to much higher compression ratios than are present in a gasoline engine. The result? Diesel engines have many more and stronger head bolts to compensate for the diesel’s higher cylinder pressure. The director of service at Caitlin Dodge of Philadelphia is familiar with the GM Diesel story and explained that the Oldsmobile diesel, however, maintained the same 10-bolt pattern and head bolts as gasoline engines, so that common production tooling could be used for both the gasoline and diesel engines. This was a faulty idea. There were other issues with the engine too: the fuel-pump timing chain stretched and several other problems occurred in addition. And, even in good running order the engines were just plain loud, and belched quite a bit of smoke all to provide acceleration that can best be described as “modest”.

Despite such problems out of the gate, production of the Oldsmobile diesel lasted from 1978 and 1985. However, the damage had been done early. General Motors ill-fated diesel caused a class-action lawsuit that saw owners reimbursed for the cost of a replacement engine upon failure. In fact, the engines were so bad, they spurred legislators in several states to draft early lemon laws. Unfortunately, in the long run, Oldsmobile diesels ruined the American consumer’s appetite for diesels for almost 3 decades. Only now are diesels beginning to reenter the U.S. car market in small numbers—and most of those are from European manufacturers. 

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