Diesel cars had some popularity in Canada over the years until Volkswagen’s “Dieselgate” emissions scandal broke in 2015 and killed the diesel market. In the United States there was less diesel enthusiasm due to lower gasoline prices. In Europe, where fuel taxes are much higher, those fuel-efficient, compression-ignition oil burners were very popular for many years.
The diesel is inherently superior to the gasoline engine in several ways, although modern technology is gradually eroding some of the differences.
A diesel’s higher compression ratio necessary to create ignition extracts more energy from the fuel. It has a higher air-to-fuel ratio and runs in a more efficient unthrottled condition because power output is regulated by fuel flow, not air flow as in a gasoline engine. And diesel oil’s calorific value is approximately 10 percent higher than gasoline. All this results in some 30 percent lower fuel consumption than gasoline engines.
Diesels didn’t enjoy early popularity in North America largely because they were smokey, smelly, noisy and slow. And the substantial engine weight penalty to withstand higher internal pressures and the high cost of close tolerance injectors relegated them mostly to commercial applications like trucks, buses and tractors.
Modern engine technology has overcome diesel’s performance shortcomings. Turbocharging and standard, fuel-rail injection make automobile diesels as powerful as gasoline engines of a few years ago while retaining their economy advantage. And their prodigious low- and mid-range torque makes them more responsive than gas engines in average driving.
The diesel engine came from the brilliant mind of Rudolf Diesel, who graduated from Technical University in Munich, Germany with the highest marks in the school’s history. Convinced of the superiority of compression ignition, he received his first diesel engine patent in 1892.
Steady improvements came, and despite industry scepticism, Mercedes-Benz introduced the world’s first production diesel car in 1936. While M-B intended the 260D primarily as a taxi where low fuel cost would offset high initial cost, they were pleased when the 260D’s durability and economy also appealed to regular motorists.
Mercedes-Benz started importing diesel cars to North America in the 1950s, but with gasoline cheap and plentiful they remained niche vehicles appealing to diesel enthusiasts and mileage fanatics. Two 1970s “energy crises” brought increased interest.
The first oil embargo in late 1973 caused by the Israel-Egypt Yom Kippur war sent demand soaring for economical cars like Hondas, Ford Pintos and Chevrolet Vegas. Manufacturers also began exploring diesels.
The oil crisis spawned fuel economy legislation in the form of the U.S. Corporate Average Fuel Economy (CAFE) standards, which Canada also followed. But consumers’ tastes are fickle and when oil crisis memories faded in the mid- to late 1970s, North American tastes began reverting to larger cars.
To meet CAFE, American auto manufacturers had begun emphasizing smaller cars. GM, for example downsized its standard size cars in 1977. With the shift in consumer preference, American auto manufacturers were forced to offer rebates to sell small cars, and had to ration V-8 engines to meet their CAFE.
When the next oil crisis arrived in 1979, carmakers were better prepared. GM had converted a 5.7 litre V-8 gasoline engine to diesel for their 1978 Oldsmobile, joining Mercedes-Benz, Peugeot and Volkswagen. Unfortunately, Oldsmobile’s diesel would have a rather star-crossed existence.
The following year brought diesels from Cadillac, Audi, Buick, Chevrolet, Pontiac and Volvo. Ten nameplates were offering diesels by 1980, with Chevrolet Chevette, Pontiac Acadian and Datsun coming in 1981.
In 1984 Ford introduced diesel Ford Escort, Mercury Lynx and Lincoln models. BMW joined the club the following year, but North American interest in diesels was already waning.
By 1986, Audi, Lincoln and Volvo had discontinued diesels, as had all General Motors cars except the Chevrolet Chevette and 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. These two outsiders disappeared in 1988, leaving Mercedes and VW.
During this rise and fall in popularity, automobile diesels underwent constant improvement. Noise was abated with better insulation and combustion control, and start-up time became virtually as quick as gasoline engines thanks to efficient combustion chamber glow plugs.
And their emissions, especially the particulates that produce the characteristic black smoke, had been largely overcome. Low-sulphur diesel oil also contributed significantly to cleaner diesels.
In sports car racing, the Audi’s R10 diesel proved every bit the equal of gasoline engines by posting multiple victories at the prestigious Le Mans, France 24-hour and Sebring, Florida 12-hour races.
With their progress in technology it would have been normal to expect diesels to be poised for a return to popularity after Volkswagen’s “dieselgate” was forgotten. Its car future, however, seems dead as the internal combustion engine is gradually being replaced by zero-emissions electric motors.