I switched to Omega fuel a couple of years ago from Coolpower to try to reduce the rust and bearing failure. I like the results that I have seen by going over to a Castor based fuel. However that being said, the castor stains that are showing up on the outside of the engine head on engines is getting pretty ugly looking (dark brown stains). What is there if anything that I can use to remove these stains??? I have tried denatured alcohol, mineral spirits, gasoline all to no avail. Any body help me???? Tnx..