1936 Mercedes-Benz 260 diesel
1936 Mercedes-Bens 260 diesel; photo courtesy DaimlerChrysler. Click image to enlarge

Story and photo by Bill Vance

The popularity of diesel-powered automobiles in North America rises and falls in reaction to the price and perceived availability of gasoline. In Europe, where fuel taxes are much higher, fuel efficient, oil-burning, compression-ignition diesels are so popular they now command about half the market.

The diesel is superior to the gasoline engine in several ways. Its compression ratio is much higher, typically twice that of a gasoline engine. It has a higher air-to-fuel ratio, and runs in a more efficient unthrottled condition because power is regulated by fuel flow, not air flow. And diesel fuel’s calorific value is approximately 10 percent higher than gasoline. These factors produce some 30 percent better economy than gasoline engines.

Why, then, have diesels not enjoyed more popularity in North America? There were also some negatives. Diesels were traditionally noisy, smelly, smoky and slow. The substantial weight penalty to withstand higher pressures, and the high cost of extremely close tolerance injectors, had relegated them mostly to such commercial applications as trucks, buses and tractors.

Modern engine technology is overcoming many of the diesel’s shortcomings. Developments like turbocharging and direct common- rail fuel injection have made automobile diesels as powerful as the best gasoline engines of a few years ago, while retaining the fuel economy advantage. They are now almost as clean as gasoline engines, and their prodigious mid-range torque makes them very responsive in average driving.

The diesel engine came from the brilliant mind of Rudolf Diesel who graduated from the Technical University in Munich, Germany, with the highest marks in the school’s history. He received his first diesel engine patent in 1892.

Steady improvement was made in the diesel, and despite much industry scepticism, Mercedes-Benz introduced the world’s first production diesel car, the four-cylinder 260D, in 1936.

M-B intended the 260D primarily as a taxi where the initial high cost could be offset by the long-distance economy. The company was pleased, however, to find the 260D’s economy and robust longevity appealing to ordinary motorists. Mercedes-Benz started importing its diesel cars to North America in the 1950s, but with gasoline cheap and plentiful they remained a niche vehicle that appealed mainly to diesel enthusiasts and mileage fanatics. It wasn’t until the oil crises of the 1970s that interest in diesel cars began to climb.

When the first oil embargo arrived in late 1973, caused by the Yom Kippur war between Israel and Egypt, demand soared for economical cars like Ford Pintos and Chevrolet Vegas. Diesels also got caught up in this frenzy. But as the oil supply returned to normal, North American motorists would gradually revert to larger, less fuel-efficient vehicles.

Consumers’ memories were short, and by the mid-to-late1970s auto manufacturers were having to offer rebates on small cars to sell them, and were rationing V8 engines to meet government fuel economy requirements. In the meantime the auto companies and government had taken the crisis seriously. The carmakers began designing smaller cars and diesel engines, and governments enacted fuel economy standards.

By the time the next oil crisis arrived in 1979, carmakers were better prepared with more compact autos, for example the GM X-cars (Chevrolet Citation, et al), and more diesels. GM had converted a 5.7 litre V8 gasoline engine to diesel and made it available in their 1978 Oldsmobile, joining Mercedes-Benz, Peugeot and Volkswagen. Unfortunately for General Motors the Oldsmobile diesel would have a rather star-crossed existence.

The following year, the diesel parade was enlarged by Cadillac, Audi, Buick, Chevrolet, Pontiac and Volvo. In all, 10 nameplates were offering diesels in 1980. Diesel availability would expand within these marques for 1981 to the Chevrolet Chevette and Pontiac Acadian. And Datsun (now Nissan) would add one.

In 1984, Ford brought out diesel versions of its Ford Escort, Mercury Lynx and luxury Lincoln models. BMW joined the club the following year, but by this time it was apparent that North American interest in Rudolf Diesel’s invention was in sharp decline.

By 1986, Audi, Lincoln and Volvo had dropped theirs, as had all of the General Motors cars except the Chevrolet Chevette and the Pontiac Acadian. A year later the diesel fraternity was back to its original Mercedes-Benz and Volkswagen members, plus the Ford Escort and Nissan Sentra. The two outsiders would disappear in 1988, leaving Mercedes and VW to carry on.

During this rise and fall in popularity, automobile diesels underwent constant improvement. In today’s models, noise has been abated with better insulation and combustion control, smoke is minimal, and start-up time is almost as quick as with gasoline engines, thanks to efficient combustion chamber glow plugs. And their emissions, especially the particulates that produce the characteristic black smoke, have been largely overcome. Low sulphur diesel oil is also contributing significantly to cleaner diesels.

In sports car racing, Audi’s R10 diesel has proved that diesels can be every bit the equal of gasoline engines by winning the prestigious LeMans, France 24-hour race, and the Sebring, Florida 12-hour race.

Despite this progress, and popularity where fuel is costly, it seems like diesel-powered automobiles will have to wait for the next oil crisis, or a dramatic rise in the price of gasoline to gain wide acceptance in North America. But more manufacturers are creeping into diesels here, such as DaimlerChrysler’s Jeep, while Volkswagen and Mercedes-Benz continue to keep the faith.

Connect with Autos.ca