CleanSump
Site Donor 2026
It cleans the piston face, at a minimum the top of the top ring, the combustion chamber, the valve faces if GDI, the intake stem too if PI. It's popular on Hyundai forums where guys are using it to help with their oil burning.Regarding the Ring Free, in a GDI engine the gasoline doesn't pass over the rings to clean them.
Don't tell them it doesn't work in a 4-stroke. Even Yamaha recommends it for 4-stroke outboards and inboards to keep rings clean.