Depends on the machine and the recs in the manual. I was raised to change oil in all tractors as close to 100 hrs. as possible. But with these newer engines burning cleaner and the recommended intervals getting longer, this is what we try to do: JD 4320, 4840, & 4960: 100 hrs JD 8200: Usually 125-150 hrs JD 8420, 9760, 9986: 250 hrs Ford 7.3 & 6.0 diesels: 4,000 miles We don't do it, but sending off oil samples every oil change, or at least once a year, seems like a really good idea to me. I need to check in to doing that this year. | 
How often between oil changes?
