Rapeseed oil can power diesel engines without difficulty in most cases.
In direct injection engines and in the presence of certain types of injector and control units, however, rapeseed oil may be unsuitable because the oil is much more viscous than diesel and should be preheated and mixed to be atomized well by the injectors.
In case of bad combustion, in fact, large deposits can form in the cylinders and the greasy part of the oil in winter can solidify, blocking the ducts.
Rapeseed oil and biodiesel
Engines need to be tuned to that particular fuel to run reliably. The old diesel engines could actually run on rapeseed oil, while in the more modern we could have problems with injection and deposits from bad combustion.