Oil change interval and vehicle mileage

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Oct 22, 2003
By Detroit
Is it possible that the oil change interval length is somewhat dependent upon vehicle mileage (as a general indicator of engine wear). So maybe a young engine (say under 75,000 miles) can run 6000 mile OCIs on dino, but a middle aged engine only 4000 miles, and perhaps an older engine (say >150,000 miles) might have to run 2000 mile intervals.
I can only accurately comment from a diesel engine perspective and after analysing a number of UOAs on my database

There is no evidence that the hours/distance on any of my heavy diesel engines have ever required shorter change intervals as they aged

This is taking UOA's results after first drain ( say 10000kms ) to final sell point at 1.2 million kms

If an engine is getting worn out and it's rings allow more blowby, then sure the oil change interval will need to be shorter. But if you've got a high mileage engine which is kept clean inside (either through the continued use of a good synthetic, or a treatment of Auto-rx) then your oil change interval can remain the same as when it was new.

In either case, this is where doing UOAs helps a lot. Doing one at least once per year will help you see if you need to adjust your OCI.
If you look strictly at wear numbers the OCI can be longer after the engine has broken in and should remain the same after that. They have for me at least.
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