Vegetable oil fuel, also referred to as straight vegetable oil (SVO) or pure plant oil (PPO), can be used as an alternative fuel in diesel engines and in heating oil burners. Due to the high viscosity of SVO, it cannot be used purely as a fuel in vehicles in most cases. Viscosity is the meaurement of liquid’s resistance to flow. There are two options for dealing with the high viscosity of SVO as a fuel in older diesel engines. The first is to add a system to the fuel line or tank to heat it up. The second is to treat the SVO with a solvent. Both methods lower the viscosity of the fuel. Some vegetable oil blends are used in unmodified vehicles, but straight vegetable oil needs specially prepared vehicles which have a method of heating the oil to reduce its viscosity and surface tension.

SVO is a first generation biofuel, meaning it is derived from a conventional source such as vegetables or food. SVO is not a biodiesel, but through the process of transesterification with methanol it becomes biodiesel.