Bel-Ray EXP Synthetic Ester Blend 4T Engine Oil Bel-Ray EXP Synthetic Ester Blend 4T Engine Oil is a 4-stroke motrocycle oil that combines the finest quality synthetic oils with select mineral base oils ensuring the highest level of protection for all 4-stroke motorcycles. Contains shear resistant VI improvers to resist viscosity breakdown. Meets the performance requirements of API SM and JASO MA2. Suitable for air-cooled/liquid-cooled 4-stroke engines and wet clutches..