The Pros and Cons of Diesel Engines

If you’re considering buying a new automobile, compare the pros and cons of diesel-powered vehicles. Consider these facts to help you decide between an engine powered by diesel fuel and a gasoline-powered one:

• PRO: Diesels get great mileage. They typically deliver 25 to 30 percent better fuel economy than similarly performing gasoline engines. Diesels also can deliver as much or more fuel economy than traditional gasoline-electric hybrids, depending on the models involved and whatever rapidly developing automotive technology achieves.

• CON: Although diesel fuel used to be cheaper than gasoline, it now often costs the same amount or more. Diesel fuel is also used for commercial trucks, home and industrial generators, and heating oil, so as demand for diesel passenger vehicles grows, the price of diesel fuel is likely to continue to rise because of competition from those other users.

  Even if the price goes up, diesel fuel would have to be 25 to 30 percent more expensive than gas to erase the cost advantage of a diesel engine’s greater fuel efficiency.

• PRO: Diesel fuel is one of the most efficient and energy dense fuels available today. Because it contains more usable energy than gasoline, it delivers better fuel economy.

• CON: Although diesel fuel is considered more efficient because it converts heat into energy rather than sending the heat out the tailpipe as gas-powered vehicles do, it doesn’t result in flashy high-speed performance. In some ways, a gasoline-powered engine is like a racehorse — high-strung, fiery, and fast — whereas a diesel engine is more like a workhorse — slower, stronger, and more enduring.

• PRO: Diesels have no spark plugs or distributors. Therefore, they never need ignition tune-ups.

• CON: Diesels still need regular maintenance to keep them running. You have to change the oil and the air, oil, and fuel filters. Cleaner diesel fuels no longer require you to bleed excess water out of the system, but many vehicles still have water separators that need to be emptied manually.

• PRO: Diesel engines are built more ruggedly to withstand the rigors of higher compression. Consequently, they usually go much longer than gas-powered vehicles before they require major repairs. Mercedes-Benz holds the longevity record with several vehicles clocking more than 900,000 miles on their original engines! You may not want to hang onto the same vehicle for 900,000 miles, but longevity and dependability like that can sure help with trade-in and resale values.

• CON: If you neglect the maintenance and the fuel injection system breaks down, you may have to pay a diesel mechanic more money to get things unsnaggled than you would to repair a gasoline system because diesel engines are more technologically advanced.

• PRO: Because of the way it burns fuel, a diesel engine provides far more torque to the driveshaft than does a gasoline engine. As a result, most modern diesel passenger cars are much faster from a standing start than their gas-powered counterparts. What’s more, diesel-powered trucks, SUVs, and cars also can out-tow gas-powered vehicles while still delivering that improved fuel economy.

Diesel technology is constantly being improved. Government pressure to produce low-emission diesel engines for passenger vehicles, trucks, buses, and farm and construction equipment has resulted not only in low-sulfur diesel fuels but also specialized catalytic converters, advanced filters, and other devices to cut down or destroy toxic emissions.