Ecological aspects, the finiteness of fossil resources and the effort to maintain the agricultural structures motivate the use of renewable materials. Since the seventies, the German Federal Agricultural Research Centre (FAL) has been dealing with the technical use of rape seed oil as alternative fuel. It was easy to demonstrate that pure rape seed oil is not suitable for long-term use in conventional diesel engines, because of the severe engine troubles that occurred. Nevertheless, the use of rape seed oil is possible if either the engine concept or the fuel is changed. Via a different combustion concept or the transesterification of the rape seed oil - mostly to rape seed oil methylester (RME) - rape seed oil can successfully be used as fuel. RME resembles diesel fuel (DF) in its physical properties. Since 1982, an agricultural tractor with unmodified engine has been running in a long term experiment at the FAL. No problems caused by this fuel have occurred. Analogously, modified engines running on pure rape seed oil must also prove their usefulness in long term tests.