The specs for my diesel motorhome say to change the oil every six months or 5,000 miles, whichever comes first. It came with conventional oil. I only drive about 3,500 miles per year. Will I cause any damage if I wait until I drive 5,000 miles before changing the oil? Can I change less often if I switch to synthetic oil?
Frank S. Winter l Manalapan, N.J.
This is a difficult question, and you’re likely to get different answers depending on which “expert” you ask. Here’s my take on the subject. As long as your engine is within its warranty coverage, you need to consider that if you have an engine problem and have no proof that you maintained the engine according to the manufacturer’s recommendations, you may have difficulty obtaining covered repairs. Once the engine is out of warranty, you can pretty much do what you want.
I understand that oil and filter changes on diesels can be costly (but so can overhauls). It’s important to consider how the engine is being used, not just how many miles it goes. If the engine is used for short trips, idles a lot, is driven in dusty conditions or has a lot of cold starts, oil change intervals should be shortened. If you tend to get in and drive several hundred miles at a time, the oil doesn’t get as contaminated and intervals can be extended.
I suggest that you have the oil analyzed when you think it is due for a change to determine just how “dirty” it is. When an engine sits, acids and moisture in the oil can do damage, and sludge will form. Oil changes should be done before storage. Synthetic oils typically do have better additive packages and can, in some cases, extend change intervals. Again, refer to the manufacturer’s recommendations.
— Ken Freund
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