Biofuel:

A number of elaborate 'dual-fuel' systems are currently on the market, allowing the use of what is essentially vegetable oil in Diesel engines. Significant modifications are necessary because the viscosity of vegetable oil at room temperature is much higher than that of petro-Diesel. Furthermore, Diesel engines running on vegetable oil are prone to 'sooting'- the build-up of deposits of partially oxidised fuel within the cylinders. This is due to vegetable oil's comparatively low cetane number.

However, the cetane number of Diesel fuel is readily enhanced, eg by addition of amyl nitrate. Viscosity modifiers have also been long-since developed by the oil industry. Development of a suitable suite of additives to enhance cetane number and cold flow properties of vegetable oil would allow them to be used to fuel Diesel engines without any modification, and render the process of converting vegetable oil to biodiesel superfluous.