Phillips 66 Type M 20W-50 is generally recommended and used as a break-in oil for newly reconditioned aircraft engines and is often used by engine rebuild and repair shops for the initial break-in of aircraft piston engines. Type M 20W-50 is designed for owners and pilots who want the performance of a mineral multigrade piston aircraft engine oil without dispersant additives.
Reduces the tendency for cylinders to glaze during running-in compared to single-grade oils.