Designed for 4-Stroke aircraft engines and Helicopter flyers who prefer a higher Oil content. 20% Nitromethane and 20% Synthetic Oil. Supplied in 5L containers not US Gallon (3.78L). Optimix-4-Stroke 20 is designed for aircraft running 4-stroke engines where 20% nitromethane is advised with 20% synthetic oil. Also works well with helicopter engines where the pilot prefers higher oil content. Good throttle response and plenty of power.