Overdrive Extra

Max Heine

Normal intervals for fluid changes

| July 29, 2011

Long-time readers are familiar with Overdrive Equipment Editor John Baxter. John has a long history of working on trucks in the U.S. Army and in later decades writing about truck technology.

We’re going to start sharing this Overdrive Extra space with John’s advice to readers who have equipment questions. If you got a query, post it as a comment here or on Overdrive’s Facebook page,

For starters, here’s one John recently answered on Facebook for Lonnie Bailey:

Q. What are the normal intervals for changing differential and transmission oils? When should you get a dyno test done? What information is gained from a dyno?

A. Lonnie, when you use synthetic lubes, it’s normally at least 300,000 miles, and may be more, like 500,000-600,000, depending on the exact specification of the fluid. Your owner’s manual should specify all details. Mineral lubes need to be changed much more often (100,000 miles at least) because they break down from the heat, and normally don’t make sense unless you need to change frequently because of contamination.

Dyno testing would normally be done when there is a question as to whether or not an engine is performing properly. A good time to do one might be after overhauling or replacing injectors, to verify that they are working properly, or after altering an engine’s power rating, to ensure the ECM was programmed properly. A dyno test might also be done to help find an engine problem that relates to poor power output.