Diesel fuel is a type of petroleum fuel that is similar to unleaded gasoline in many respects. Both have the same core ingredient of petroleum, and both are used to power vehicles. Diesel is different in some key aspects, however, which means that a vehicle can usually run on only one or the other of the fuels.
Denser than unleaded gasoline, diesel fuel is more fuel efficient overall. Although some people think it releases more greenhouse emissions, it actually releases less greenhouse gas for the distance traveled. This is because the increased emissions — which are about 15% higher — are more than offset by the increased fuel efficiency of diesel engines — which are about 30% more efficient on average.
Greenhouse gasses are not the only thing to take into consideration when considering the cleanliness of a fuel. Diesel fuel does tend to have relatively high levels of sulfur, which can lower vehicle efficiency, and allow more particulate matter to escape filters. It is also known to have considerably worse performance than unleaded gasoline in cold weather, although some modern vehicles have taken steps to compensate for this.
In the past, especially in the United States, diesel fuel was considerably dirtier than unleaded gasoline. Vehicles in the United States also tended to be built for traditional gasoline, with the exception of large trucks, buses, and semis. In recent years, however, steps have been taken to improve the cleanliness of the fuel through regulation, and many companies have begun selling popular consumer cars that run on diesel.
In addition to actual diesel fuel, which is often referred to as petro-diesel to highlight the fact that it is made from petroleum, there are a number of diesel fuels that are made from alternative sources. The diesel engine was originally conceived of as a way to run vehicles off of vegetable oils, in an effort to allow small farmers to compete with large oil companies in selling fuel. Although this effort didn’t take off at the time, in recent years there has been a resurgence of interest in food-based fuels.
Biodiesel is the most common name for this type of fuel, and it offers many benefits over both unleaded gasoline and traditional diesel. It can be made from any sort of vegetable oil or animal oil, and many people use waste oils from restaurants or home use to fuel their vehicles. With minimal work, raw biodiesel can be used with existing diesel engines, and conditioned biodiesel can be used as is. Many people look to biodiesel as a short-term alternative to traditional petro-fuel sources, including both diesel fuel and gasoline, touting its environmental, political, and economic benefits.