wow Harley oil in an airplane. Harley oil is basically the same oil used in diesels in fact if you look at a Harley owners manual if you can't get Harley oil they say in a pinch substitute diesel oil. Its in my 2007 1200 sportster manual. Now for the legality of the issue its plain and simple a violation of the FARs to use an non approved oil in an aircraft engine. In fact its illegal to use marvel mystry oil in an aircraft engine but lets not go there. In the event of an engine failure my guess the insurance company would have a pretty good case for not paying. The other issue Harley oil is about five bucks a qt I pay $68 a case for aeroshell go figure. Even if its compatable its not approved.
Len
