SEMI-SYN is a complex blend of synthetic esters and highly refined petroleum base stocks offering protection beyond conventional oils. Technologically advanced additives containing special anti-wear/extreme pressure additives protect critical engine components from extreme loads and peak temperatures generated by high-performance engines. Advanced, shear-stable polymers resist mechanical break-down and viscosity loss of the oil. SEMI-SYN delivers increased horsepower, optimum engine cleanliness, reduces wear on bearings, cams, lifters, crankshafts and extends engine life. High Zinc/Phosphorous formula engineered for use in flat tappet and roller element engines.