AeroShell Oils W80, W100 and W120 are ash less dispersant oils 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 are SAE 40, SAE 50 and SAE 60, which equates to AeroShell Oil W80, W100 and W120 respectively. Traditionally, the choice is associated with climatic zones - AeroShell W80 for cold climate regions (-17 - 21 Degree C).