Bel-Ray Thumper Racing Synthetic Ester Blend 4T Engine Oil Bel-Ray Thumper Racing Synthetic Ester Blend 4T Engine Oil is a 4-stroke motorcycle racing oil that combines the finest quality synthetic esters and highly-refined mineral base oils specifically engineered for today's 4-stroke single cylinder, multi-valve racing engines. Provides maximum anti-wear protection for valve-trains, rings, cylinders and pistons. Delivers maximum horsepower while providing consistent clutch performance. Meets API SN and Jaso MA2 requirements. Suitable for air-cooled/liquid-cooled 4-stroke engines and wet clutches. Features: Synthetic ester blend for racing engines that need maximum horsepower and consistent clutch performance Wear protection for valve-trains, rings, cylinders and pistons For air-cooled/liquid-cooled 4T engines with race clutches API SN, certified Jaso MA2