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 formulate their 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. The Red Line 15W50 is the ultimate high-temperature protection engine oil that is recommended for street use. Good for engines that regularly run very high oil temperatures. Best for engines that run large clearances such as air-cooled engines or large-displacement, all-out racing engines that see occasional street use. Provides 25% more viscosity in bearings than petroleum 15W-50s. Not recommended for use in cold climates where temperatures are at or below 10 F or -12 C. Not recommended for street use in production engines that see sustained oil temperatures below 225 F (those engines should use Red Line 10W-30 or 10W-40).