Phillips XC 20W-50 Aviation Oil is the first approved multiviscosity aviation oil for opposed piston engines. It provides better engine performance than any single-grade oil in all weather conditions. XC 20W-50 is formulated with an ashless dispersant package allowing for cleaner engine operation. X/C 20W-50 is recommended for break-in. It provides a cleaner and quicker break-in than traditional all mineral single grade oils. Plus, X/C®is an operational oil so there is no need to switch oils after break-in. X/C 20W-50 utilizes all petroleum base oils which provide excellent solvency and is successful in preventing lead and lead salts.