What You Should Know About Diesels

Diesel engines are similar to gasoline engines, but they don’t have spark plugs. Instead, a diesel engine compresses the air in each cylinder until it is hot enough (more than 1,000 degrees Fahrenheit) to automatically ignite the fuel that is injected. This high compression ratio makes diesel engines very efficient. In addition, diesels can operate with very lean air-fuel mixtures, particularly at idle, and diesel fuel contains more energy per gallon than gasoline. Taken together, these factors allow diesel engines to get much better fuel economy than comparably sized gasoline engines.

Diesel fuel requires less refining than gasoline, which used to mean it was less expensive. However, since 2004, increasing worldwide use of diesel fuel coupled with refining capabilities that have trailed demand have resulted in diesel fuel costing more than gasoline. Still, because it contains more energy per gallon, diesel fuel remains a better value.

All 2007 and newer on-highway diesel-powered vehicles use ultra-low sulfur diesel fuel that contains 97 percent less sulfur than older diesel fuel. USLD has enabled the use of advanced emission control systems, and modern “clean diesels” meet the same exhaust quality standards as their gasoline counterparts. Forget that image you may have in your mind of smelly black smoke billowing from a tailpipe and covering everything in soot. Today, the exhaust from a diesel is nearly indistinguishable from that of any other engine.

Something you will notice about diesels the first time you drive one is how they deliver power. A gasoline engine needs to be revved and produces more horsepower at a higher rpm. Diesel engines are slower-turning and produce more torque at low rpm. Torque is the twisting force provided by the engine crankshaft that actually does the work of moving the car down the road. With more torque, diesels typically have good off-the-line acceleration and provide passing power without the need for frequent transmission downshifts.

Modern diesel engines not only offer excellent fuel economy, they are cleaner and greener than most people realize. In addition, the power delivery characteristics of diesels make them well-suited to hauling loads or towing trailers.