Any fuel used in a diesel engine is called diesel fuel. These fuels are classified as 1D, 2D and 4D. A main difference between these is the pour point, the lowest temperature a liquid will flow. A second difference is viscosity, the resistance of a liquid to flowing. Most diesel fuels are made of petroleum, but other types are available such as biodiesel and synthetic diesel.
4D fuels are only used in very low-speed engines such as those in stationary units or marine operations.
1D diesel fuel has lower viscosity and a lower pour point than 2D, so is preferred for cold weather.
1D diesel fuel has only about 95 per cent of the energy output as 2D, causing reduced gas mileage and lower horsepower.
2D fuel is used in warmer weather, and also can be mixed with 1D for an effective winter fuel.
Another type of diesel fuel is biodiesel, obtained from vegetable oil or animal fats. Some versions can be mixed with petroleum diesel.
Synthetic diesel fuel is derived from various sources such as wood, straw, corn and even garbage and food scraps.