Mobil Jet Oil 387 approved for use in Rolls-Royce engines ExxonMobil Press Release | April 7, 2021 Estimated reading time 3 minutes, 32 seconds. ExxonMobil has announced that Mobil Jet Oil 387 is approved for use in Rolls-Royce M250 and RR300 engines which are most commonly found in helicopters. The Rolls-Royce M250 is one of the most popular turbine engines in the world with over 170 different helicopter and fixed-wing applications in both civil and military aircrafts. Helicopter engines are high temperature applications and require jet oils that provide excellent seal compatibility. As ExxonMobil’s most advanced aviation turbine engine oil, Mobil Jet Oil 387 provides superb seal compatibility and prolonged life, offering protection against oil leaks. Mobil Jet Oil 387 also offers outstanding deposit control and oxidative stability, as well as improved load carrying compared to other legacy High Thermal Stability (HTS) oils.