I noticed more carbon after just a few minutes bench time while running motor oil in my four strokes. I think that some additives might improve this. I thought about adding some Diesel Kleen to try it out. I had some early on before I found Amsoil ACB locally. I did run some fuel with the Diesel Kleen but I was concentrating on making the thing run rather than deposits. After I found ACB, I gave the DK to my father to burn in his 5.9L. With Maxima Castor I have just a light film that wipes off.

That should have been 5.9L!