Originally Posted By: UltrafanUK
Extending an OCI without a UOA is not a good idea. I would get a UOA done at 5000, 7500 and 10,000 miles to make sure the oil is still good. If you get a sample pump (Blackstone Lab do sell them) there is no need to change the oil at the intermediate steps.
Once you have the figures then check to see what the Iron figure per mile is to see if the engine likes the longer OCI or not.
Don't think that you can extend an OCI just because full synthetics are more resistant to high temp shearing, as it is more likely that contamination will limit the OCI.
Good points. Many people buy into blanket statements like synthetic oils can go 10K miles easily. Maybe, maybe not, the only way to know for sure is with a UOA. Those kind of statements can get you in trouble, especially if you live in an area like NYC or Long Island for example. During a rush hour commute a 20 minute ride can take anywhere from 45 minutes, if you're lucky, to 90 minutes or more. That's a lot of engine run time to cover such a short distance.