Diesel fuels are broken up into 3 different classes: 1D(#1), 2D(#2) and 4D(#4). The difference between these classes depends on viscosity (the property of a fluid that causes a resistance to the fluid’s flow) and pour point (the temperature at which a fluid will flow).
#4 fuels tend to be used in low-speed engines. #2 fuels are used in warmer weather and are sometimes mixed with #1 fuel to create a competent winter fuel. #1 fuel is preferred for cold weather as it has a lower viscosity. It used to be standard to see the fuel # on the pump, but a lot of gas stations do not state the fuel number anymore.
Another important factor is the rating of Cetane in the diesel fuel. Cetane is similar to Octane for gasoline fuel and it indicates how easy the fuel will ignite and burn. Since Ultra low Sulfur diesel fuels became standard in the middle 2000s, the cetane has been reduced which makes the newer fuel less desirable for diesel enthusiasts. It is highly recommended to run a fuel additive to increase the overall Cetane number. Diesel fuel additives such as Fuel Bomb will also have lubricity additives which will help the modern diesel engine run better and achieve a higher fuel economy(MPG). One other feature of a diesel fuel additive is that it does not need much per tank. A standard bottle of diesel fuel additive usually treats 250-500 gallons.
Here is an article from Diesel Power Magazine on diesel fuel additives and why they are important.
Synthetic diesel comes from several sources such as wood, straw, corn and even garbage or discarded foods.
Biodiesel is an ecologically-friendly type of diesel. It is a cleaner-burning diesel made from natural, renewable sources such as vegetable oils and animal fats. Biodiesel is helping to reduce American dependence on foreign petroleum. It is also helping in the creation of green jobs and the improvement of our environment.