Originally Posted by MCT

I know of folks who use Marvel Myster Oil to keep the top end clean of carbon deposits and the valve guides lubricated but never two-stroke oil. That would cause the opposite and increase deposits.

Marvel Myster Oil, though not approved in aircraft use, was and still is popular with folks who have older aircraft engines that were originally designed for low octane fuel. It is believed to help scavenge the carbon out of the cylinder and, again, keep the valve stems clean and lubricated. MM Oil has been analyzed as a mild solvent. It can be used in the oil, (top end), and the fuel, (cylinder and intake), but that is up to the owner.