Magazine article Consumers' Research Magazine

Will Diesel Engines Make a Comeback? Energy Efficient and Now Less Dirty

Magazine article Consumers' Research Magazine

Will Diesel Engines Make a Comeback? Energy Efficient and Now Less Dirty

Article excerpt

What is the truth about diesel engines? Are they inherently dirty? Do they belch clouds of black soot? Are they unsuited to cars, as evidenced by 1980s class-action suits against GM's diesel "lemons?" Do they make an unnecessary racket when idling and accelerating? Are their emissions toxic and a threat to human health? Many ask, in this age of ultra-clean transport, why do we still have diesel engines? The governor of Tokyo and air quality regulators in southern California have both launched campaigns to ban them.

But there's another side to the story of diesel engines. European regulators assert they are an answer to climate-change threats. Many automotive companies claim that new diesel engines are dramatically improved and as clean and quiet as gasoline engines. And freight companies rely almost exclusively on diesel engines for their trucks because they are durable and efficient. Indeed, diesel engines continue to increase their market share worldwide, now accounting for about 40% of all roadway fuel consumed.

Diesel engines have come to play major roles in our freight transport system. They have powered almost all heavy-duty trucks and most transit buses for decades, for good reasons. They are more fuel efficient, durable, and reliable than gasoline engines; they require less maintenance, provide high torque for moving heavy loads, and, in high-mileage vehicles, tend to have lower life-cycle costs. The cost advantage is especially crucial to the freight industry. Indeed, until the tightening of heavy-duty engine emission standards in the late 1980s, diesel-engine use in trucks and buses was accepted as unquestionably positive. Even now, despite growing controversy about their health effects, diesel engines continue to gain prominence. They doubled their share of total roadway fuel use in the world in the past 25 years, and the percentage continues to increase.

Diesel History and Status. Diesel engine use has been most controversial in the United States. Mercedes had been producing diesel cars for many years, but in the mid-1970s, in response to skyrocketing fuel prices and newly imposed fuel-economy standards, a number of other manufacturers began producing diesel cars. Market penetration increased to 6.1% of light-duty vehicle sales by 1981. But one manufacturer was too quick getting to market. One of the GM diesel car engines, a 5.7-liter engine converted from truck use, turned out to have many widely reported problems. GM spent large amounts of money vainly trying to fix the engine, settling class-action lawsuits, and dealing with complaints to the Federal Trade Commission.

Because of that bad experience, and also because diesel-fuel prices in the U.S. increased around that time to rough parity with gasoline prices and have remained at that level, no automaker has aggressively promoted diesel cars since. A recent resurgence of interest in light-duty diesels reflects steady improvements in noise and emissions and automakers' difficulty meeting the national 20.7 mpg fuel economy standard for gasoline-fueled light-duty trucks (applicable to vans, pickups, and sport utility vehicles). Diesel engines are now being introduced in small numbers in pickups and other light-duty trucks. Diesels account for 0.1% of automobile sales (with Volkswagen the only supplier) and approximately 4% of light-truck sales in the U.S.

The contrast with Europe is striking. There, diesel cars now account for over 30% of sales--over 50% in some countries---and the percentage continues to climb. Aided by low diesel-fuel prices, relatively gentle regulatory treatment of diesel car emissions, and aggressive carbon dioxide emission goals, diesel cars are likely to exceed 40% of European vehicle sales within a decade.

Truck and Bus Emissions--Past and Present. Diesel engines produce much lower levels of carbon monoxide and hydrocarbons than do gasoline engines, but much higher levels of nitrogen oxides and particulate matter. …

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