Fatty Acid Methyl Ester (FAME) is the primary constituent of biodiesel. A certain percentage of FAME in forecourt diesel fuel is allowed (currently up to 7%), however not all engines are able to cope with greater concentrations. Determining the biodiesel content of the fuel may be necessary to diagnose engine failure. Some of the problems caused include “corrosion of fuel injection components, low-pressure fuel system blockage, increased dilution and polymerisation of engine oil, pump seizures due to high fuel viscosity at low temperature, increased injection pressure, elastomeric seal failures and fuel injector spray blockage”.