When we talk about fuels, we commonly mean liquid fuels like petroleum (diesel, petrol, kerosene, etc.). Other types of fuel include solid fuels (coal, wood, dung, etc.) and gaseous fuels (natural gases such as propane, coal gas, water gas, etc.). As far as liquid fuels are concerned, one of the most important factors influencing their consistency, besides pressure, is temperature. Diesel and petrol, for example, are exposed to a wide range of temperatures, depending on the climatic conditions. In order to remain liquid, even at very low temperatures, their freezing point must be lower than the service temperature or rather the ambient temperature. It can be generally stated that petrol has a lower freezing point than diesel fuel. In order to depress wax precipitation, additives are frequently used to improve fluidity of fuels even at low temperatures.