Good catch on the bio diesel.

I would also like to add that a diesel - any diesel - runs better after it has been worked or driven in ways that provide a fair amount of EGT over a long enough period of time to burn some of the carbon buildup on injector nozzles. Even my Duramax runs better after a few hundred miles of Interstate, that includes a few mountain passes.

So... adding oil to the fuel may increase the carbon buildup on injectors in a lightly loaded diesel engine, especially those that are used locally and in cooler temperatures.