The good and the bad about diesels

To accurately compare diesel engines with traditional gasoline-powered vehicles, you need to consider a number of pros and cons.

PRO: Diesesl get great mileage.

CON: So do vehicles with fuel-efficient gasoline-powered engies, which often cost a couple of thousand dollars less than diesels. You can buy a lot of gas for a couple of thousand dollars!

Diesel fuel is not available at many service stations, and although is used to be cheaper than gasoline, it now often costs as much more - or more - than gasoline, and it may become even more expensive, depending on availability and demand.

PRO: Diesel fuel contains more usable energy than gasoline.

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 performance." A gasoline-powered vehicle is like a racehorse - high-strung, fiery, and fast - whereas a diesel vehicle is more like a workhorse - slow, strong, and (hopefully) enduring.

PRO: Diesels have no spark plugs or distributors. Therefore, they never need a tune-up.

CON: Diesels still need regular maintenance to keep them running. You have to change the oil and the air, oil, and fuel filters, and you may need to bleed excess water out of the system. This chapter shows you how to do these things yourself, but if you neglect the maintenance, and the fuel injection system breaks down, you'll probably have to pay a diesel mechanic big bucks to get things unsnaggled.

PRO: Diesels are build more ruggedly to withstand the rigors of higher compression. Consequently, they usually go much longer before they require major repairs than conventional vehicles do. (Mercedes-Benz holds the longevity record with several vehicles clocking more than 900,000 miles on their original engines!)

CON: Do you really want to hang on the same vehicle for 900,000 miles? Also, there have been cases where automakers have simply plunked diesel engines into vehicles that were originally designed to be gasoline-powered. Because there vehicles weren't constructed to stand up to the stress imposed by the high compression that diesel engines require, they suffered failures that contributed to their swift decline in popularity.

PRO: Turbocharged diesel have better fuel efficency and are much more powerful and responsive than traditional diesel vehicles.

CON: Turbocharging will probably get cheaper and even more efficient as time goes on, but you can buy a turbocharged, gasoline-powered vehicle and have the advantages of both.

PRO: Diesel have become easier to start in cold weather.

CON: Although they're better than they used to be, diesel engines are still more difficult to start on cold days than gasoline engines are.

PRO: Diesels put out much less carbon monoxide than ordinary vehicles do, which means less air pollution.

CON: This is a major misconception. Diesels put out 30 to 90 percent more nitrogen oxides and carbon particles (soot), and recent studies show that diesel emissions can cause cancer. As a result, recent legislation is aimed at getting diesel-powered vehicle off the road completely unless they can find a way to meet increasingly stringent EPA standards.

By the time you read this book, the diesel pros and cons may have changed. Government pressure to produce low-emission diesel engines for trucks, buses, and farm and construcion equipment by the early 2000s has resulted in increased efforts to develop low-sulfur diesel fuels, specialized catalytic converters, and advanced filters and other devices to cut down or destroy toxic emissions, as well as dual-fuel engines that run on natural gas but can switch to diesel if the gas supply runs out.