Stihl four mix engines are indeed a four stroke with valves set to four thousands. Really only need setting if it gets hard to pull over o tries to rip the starter handle out of your hand. They were made for emissions and extra torque. There is no oil per say in the CC but it circulates everywhere while running. Uses the same 50-1 ratio so there is no confusion on owners part. Big benefit is they are impossible to wear out and I never saw one seize from running straight gas for many tank fills.