The refining companies are well aware of the starting problems associated with diesels in cold weather, and they usually “winterize” their diesel fuel by mixing 15-20 percent No. 1 diesel with the conventional No. 2 diesel in cold climates. This improves the volatility of the fuel and reduces the cloud point to slightly lower temperatures. At this point, we should discuss the differences between the two grades of diesel fuel. Diesel No.1 and No.2 are the two common grades of diesel fuel. No. 2 diesel is by far the most widely used since it provides the most energy per gallon for improved power and mileage, and the highest lubricity for the fuel injection pump. Since it is a heavier distillate than No. 1 diesel, No.2 diesel is usually a few cents per gallon cheaper too. Some diesel engines are designed to operate specifically on No. 1 diesel, especially if the engine will be subjected to frequent starting and stopping, but No.1 diesel has several disadvantages. First, it provides less lubricity than No. 2 diesel, which can prove troublesome for some fuel injection pumps, and second, it contains roughly 95 percent of the heat energy of No. 2 diesel.