Red Line's 10W40 Synthetic Oil is the best choice for engines that typically run high oil temperature or for engines in daily-driven vehicles regularly operated in hot weather. It is great for medium and heavy duty gasoline engines in trucks and is the best choice for high-performance engines that see street/strip or track activity. It features a thicker oil film at operating temperature than a petro-based 20W-50. Red Line's synthetic motor oils are designed to provide the highest protection, cleanliness and superior drain intervals with the lowest friction for your gasoline, diesel, motorcycle or marine engine. Red Line uses the most stable components available and formulates products for wear protection and friction reduction across a wide range of engine operating conditions. Red Line's products are unique because they contain polyol ester base stocks, the only lubricants which can withstand the tremendous heat of modern jet engines. These synthetics have a natural multigrade property which allows our chemists to avoid bulking up an oil with unnecessary additive packages. Red Line Synthetic Motor Oils are designed to provide the highest degree of protection and cleanliness for your engine. Red Line uses the most stable synthetic components available and formulates their products for wear protection across a wide range of operating conditions. Red Line lubricants contain polyol ester basestocks, the only lubricants which can withstand the tremendous heat of modern jet engines, which makes our motor oil a necessity to properly lubricate a turbocharger or hot-running engine. The synthetic basestocks have a natural multigrade property, which means that large amounts of unstable polymeric thickeners are not required to manufacture our multigrades. Red Line Synthetic Motor Oils will provide better protection than a petroleum oil of the next higher viscosity grade under high shear conditions.