Long ago when I worked in the Chain saw industry it was rare that a saw piston did not contain some carbon. Back then we didn't recommend synth oils and this was a contributer to the carbon deposits. The measurable loss do to the carbon was Nil in my opinion. We did have a generator that would develope excessive carbon and the result was that it would Deisel and not turn off. The Chain saw guys would put a lot more hours on their saws that we do on our planes for the most part so I doubt you will see too much carbon. Just my .02.