Grades of Diesel

Two types of diesel fuels are used in cars and trucks: No. 1 and No. 2. The American Society for Testing and Materials (ASTM) classifies these two grades. In the distillation process, No. 1 diesel fuel has a lower boiling point than No. 2 and thus vaporizes easier than No. 2. Therefore, No. 1 diesel fuel is commonly used when the outside ambient temperature is abnormally low. In cold climates many gas stations commonly provide No. 1 in the extreme winter, a mixture of No. 1 and No. 2 in the fall and spring, and No. 2 in the summer. No. 2 diesel fuel has a tendency to “gel” in severely cold climates.