SVO, or Straight Vegetable Oil, can be used to fuel a diesel engine. The engine requires no modifications, but natural-oil fuels tend to become solid at relatively high temperatures. Therefore, the fuel must first be heated to ensure that it has a viscosity similar to that of diesel.

At the time of its invention in 1895, the diesel engine was designed to operate on natural-oils, such as peanut and vegetable oil. The idea of using a petroleum-based fuel was later developed because it was cheap and plentiful. The level of engineering involved in designing an effective and problem-free pre-heating system has often been thought to be cost-prohibitive, when compared with the simplicity of using petroleum-based diesel fuel. However, due to rising petroleum prices and environmental concerns, many are revisiting the possibility of vegetable oil and VO based fuels in vehicles (and other applications). Therefore, this too is an area undergoing great and exciting development right now.