1978 Oldsmobile Regency 98 diesel; photo courtesy General Motors. Click image to enlarge

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By Bill Vance

Although diesel engines are more efficient and economical than gasoline engines, the clatter, smell and smoke of earlier models found little favour with North American motorists until the 1970s when energy crises threatened gasoline supplies. And even then, their popularity in cars was fleeting.

In Europe, where fuel is much more expensive, motorists enthusiastically embraced the oil sipping diesel. Daimler-Benz introduced the world’s first diesel production car, the Mercedes-Benz 260D, in 1936. Although meant for taxi use, the 260D’s economy and durability appealed to ordinary motorists and Daimler-Benz became a strong diesel car advocate.

The diesel engine was the brainchild of Rudolf Diesel, a brilliant German engineer born in 1858. In 1892, Diesel received a patent for his “rational heat engine.” He was determined to produce a more efficient powerplant than the then dominant steam engine.

While the steamer was an external combustion engine which burned its fuel outside the engine, the diesel, like the fledgling gasoline engine, burned fuel inside the cylinders. But unlike a gasoline engine which ignited its fuel with a spark plug, diesel combustion occurred by injecting the fuel oil, or kerosene, into the cylinder where it was ignited by the heat of a very high compression ratio. The diesel, therefore, is technically called a compression-ignition engine.

Although a despondent Diesel committed suicide in 1913 by jumping overboard into the English Channel, others carried on and gradually evolved the diesel into the most efficient stationary engine available. In the 1920s experiments were conducted with diesel cars, and in the 1930s diesels appeared in large mobile applications like locomotives and line-haul trucks.

While Europe enthusiastically adopted diesel cars, cheap gasoline kept them off the North American scene. There were some disciples, however. In 1930 Clessie Cummins, a diesel engine manufacturer in Columbus, Indiana, installed one in a 1925 Packard, the first such U.S. application. Cummins demonstrated its economy by driving from Columbus to the New York Auto Show on $1.38 worth of fuel oil!

The Auburn Automobile Co., of Auburn, Indiana, considered offering a Cummins diesel option in 1935, but the company’s early demise ended that plan. It would be over 40 years before an American manufacturer would offer the first diesel powered car.

The impetus for an American diesel was the energy crisis of 1973-’74 which resulted in Corporate Average Fuel Economy (CAFE) legislation requiring auto manufacturers to achieve a sales weighted fleet average of 18 mpg (U.S.) in 1978 models, rising to 27.5 in 1985.

General Motors saw the diesel engine as a major contributor to meeting this requirement, and in 1978 Oldsmobile offered the first American diesel powered car. It spread to other large GM cars in 1979.

To create the diesel, Oldsmobile used its 5.7-litre (350 cu in.) pushrod gasoline V8 as a base. Since a diesel’s internal pressures are much higher than a gasoline engine’s – its compression ratio was typically twice as high – the V8 had to be substantially reinforced. Stronger bearings, pistons and connecting rods were developed, as well as a stouter crankshaft and cylinder block.

The new cylinder heads were fitted with glow plugs to aid starting, and it had pre-chambers where combustion was initiated by a richer fuel-air mixture and then spread to a leaner charge in the main combustion chamber.

Unfortunately when the diesel reached the public’s hands, problems surfaced, including blown head gaskets, oil leakage and even crankshaft and piston failures. Apparently the conversion from gasoline to diesel had not been wholly successful, and in the early 1980s Consumer Reports magazine consistently advised readers to avoid GM diesels.

The GM diesel was gradually brought to a higher level of reliability. When it was running perfectly it was, as Car and Driver magazine (12/’77) said, “…the only way to haul six people 600 non-stop miles in shameless comfort on sixteen bucks’ worth of fuel.”

But although it was economical, performance was modest. C and D reported that its 120 horsepower took 14.9 seconds to haul the 1,887 kg (4,161 lb) Delta 88 sedan up to 96 km/h (60 mph). Top speed was only 150 km/h (93 mph).

In mid-1981 General Motors introduced a 1.8-litre Isuzu four-cylinder diesel in its sub-compact Chevrolet Chevette/Pontiac Acadian. For 1982, Oldsmobile brought out a 4.3-litre V6 diesel, a three-quarter version of the 5.7 V8. In 1984 Ford would offer a diesel in its small Ford Escort/Mercury Lynx.

In addition to the American nameplates, diesels were offered by, Audi, Mercedes-Benz, Peugeot, Volkswagen and Volvo.

By the mid-1980s fuel concerns were gone and diesel cars quickly faded from the North American scene. Only Mercedes-Benz and Volkswagen carried on, and the M-B diesel was quietly dropped here in 1999, although it did come back. Volkswagen still carries on the compression-ignition torch, and others such as BMW are joining.

Although modern automobile diesels have vastly improved refinement, performance and cleanliness, the relatively low price of gasoline still leaves them as niche players in the North American market.