Most manufacturers recommend an early initial oil change after the transmission is placed in service when using mineral-based gear lubes. It is usually recommended that this first oil change be made any time after 3,000 miles but before 5,000 miles of linehaul road service. In off-highway use, the first transmission oil change should be made after 24 and before 100 hours of service. Although transmission oil is never required to be changed as frequently as engine oil, this first oil change is important because it will flush out of the transmission any cutting debris created by virgin gears meshing.
A number of factors influence the appropriate scheduling of mineral-based transmission oil change periods. A key factor is the application: Linehaul operation tends to be kind to transmission oil, whereas operating on a construction site can reduce performance life. Depending on the transmission, manufacturer suggestions for mineral-based transmission oil change intervals vary between 50,000 and 100,000 miles for linehaul applications. However, for purposes of this textbook, the Eaton recommended mineral oil change interval of 60,000 linehaul miles is referenced. Off-highway operation usually requires oil change intervals ranging from 1,000 hours to a maximum of 2,000 hours of service. In each housing, the type of oil used can influence the oil change interval. Practice shows that using synthetic lubricants can greatly extend the performance life of the oil.