Diesel

Product Details

diesel fuel, also called diesel oil, combustible liquid used as fuel for diesel engines, ordinarily obtained from fractions of crude oil that are less volatile than the fractions used in gasoline. In diesel engines the fuel is ignited not by a spark, as in gasoline engines, but by the heat of air compressed in the cylinder, with the fuel injected in a spray into the hot compressed air. Diesel fuel releases more energy on combustion than equal volumes of gasoline, so diesel engines generally produce better fuel economy than gasoline engines. In addition, the production of diesel fuel requires fewer refining steps than gasoline, so retail prices of diesel fuel traditionally have been lower than those of gasoline (depending on the location, season, and taxes and regulations). On the other hand, diesel fuel, at least as traditionally formulated, produces greater quantities of certain air pollutants such as sulfur and solid carbon particulates, and the extra refining steps and emission-control mechanisms put into place to reduce those emissions can act to reduce the price advantages of diesel over gasoline. In addition, diesel fuel emits more carbon dioxide per unit than gasoline, offsetting some of its efficiency benefits with its greenhouse gas emissions.

Several grades of diesel fuel are manufactured—for example, “light-middle” and “middle” distillates for high-speed engines with frequent and wide variations in load and speed (such as trucks and automobiles) and “heavy” distillates for low- and medium-speed engines with sustained loads and speeds (such as trains, ships, and stationary engines). Performance criteria are cetane number (a measure of ease of ignition), ease of volatilization, and sulfur content. The highest grades, for automobile and truck engines, are the most volatile, and the lowest grades, for low-speed engines, are the least volatile, leave the most carbon residue, and commonly have the highest sulfur content.