Must have taken Stihl a long time to develop those 4 mixes:
"RedMax is the original inventor of the world’s first stratified-charged 2-stroke engine.
Introduced in 1998, our state-of-the-art Strato-Charged engines are designed with advanced technology that reduces impact on the environment through efficient engine design, increased fuel economy and reduced emissions.
For ten years, this proven technology has delivered maximum performance in a light, rugged design with outstanding features that set it apart from the competition. The Strato-Charged 2-stroke engine:
Achieves up to 20% more fuel efficiency than standard 2-stroke engines Produces low emissions that meet regulations without the need for a heated, heavy catalytic converter Requires no valve adjustments, oil changes or daily oil reservoir level checks Generates 15 to 20% more horsepower than a typical 4-stroke or 4-stroke hybrid engine of the same engine displacement size Includes the hallmarks of RedMax engineering and design: MaxPower, MaxTorque, MaxSpeed, MaxAcceleration, MaxPerformance and MaxTechnology RedMax’s Strato-Charged 2-stroke engines operate at maximum efficiency with just three moving parts. By comparison, 4-stroke or 4-stroke hybrid engines contain as many as 30 moving parts."