Originally Posted by RamblerGuy
If you want to extend your oil change intervals you can have the oil analyzed. The lab can tell you if you need to or not, and will tell you if there are excessive contaminants or wear particles in the oil. Years ago it wasn't worth it for cars, but the cost of synthetic oils and very expensive filters for diesels may make it worthwhile. Many small airplane owners do this to watch for unusual wear, not to extend oil change intervals.
I don't know of a lab but you could find some on the internet.
I used them when I had my diesel. Test results are interesting and can give you a good baseline if done when the engine is new. Subsequent tests can be compared to see if there is any unusual wear occurring vs universal averages and your own previous tests.