Fuel testers analyze the properties and composition of biofuels, gasoline, diesel, and petroleum-based fuels and fuel feedstocks. Product specifications include tested fuel type, device features, and properties analyzed. Some fuel testers are designed to sample biomass fuels (biofuels) derived from switchgrass, vegetable and plant oils, or other living organisms. Other fuel testers are designed to test fuel blends such as E85 ethanol, a common U.S. blend of approximately 85% denatured fuel ethanol mixed with gasoline or a similar hydrocarbon. International standards for fuel testers are defined in ASTM D6890, IP 498, and EN 15195. 

Most fuel testers are designed to test fuels made from alcohol or ethanol, butane, coal, diesel or biodiesel, naphtha, propane, and natural gas or methane. Fuel testers for aviation fuel or jet fuel, gasoline, fuel oil, hydrogen, naphtha, and wood are also available. Diesel fuels are made from petroleum or from natural sources such as vegetable oils or animal fats (biodiesel). Fuel oil is a fractional liquid fuel derived from petroleum distillation and burned in furnaces or boilers to generate heat. Hydrogen fuels are relatively non-polluting and often used with solid oxide fuel cells (SOFC). Fuel testers for other fuels are also available. 

Fuel testers are often used to analyze properties such as blend composition, cloud point, energy density, and flash point. Blend composition testing determines the relative amounts of constituent materials on a percent mass or percent volume basis. Cloud point (CP) is the temperature at which the dissolved solids in a sample separate out. Energy density is the amount of useful energy stored in a given sample. Flash point is the lowest temperature at which a liquid can form an ignitable mixture in air near the surface of the liquid. 

Some fuel testers are designed to determine a fuel’s octane or cetane rating, pour point, stability, or total base number. The octane rating or number indicates the resistance of gasoline or ethanol to early detonation, which causes engine knocking. Cetane numbers or ratings are used on diesel or biodiesel fuels that combust through compression. Pour point is the lowest temperature at which a liquid fuel will pour or flow under prescribed conditions. Total base number (TBN) refers to a fuel’s reserve alkalinity or to the amount of acid the oil or lubricant can absorb.