AeroShell Oil W120 is an ashless dispersant oil specifically developed for aviation piston engines. They combine non-metallic additives with selected high viscosity index base oils to give exceptional stability, dispersancy and anti-foaming performance. No general rule exists for every engine type when choosing the correct grade of oil; however, based on the average ambient outside temperature at engine start-up the most common grades is SAE 50 which equates to AeroShell Oil W100 respectively.