Having an oil analysis is the only real way to determine how long you should go with your oil changes. Expense becomes the issue here. I am confident we can go 5000 miles without a problem. Have your oil analyzed at 5K and check the results. Many labs will give you a read out of everything that is checked with results, then a summary is written of what needs to be checked or repaired/changed. If good at 5K, have it checked again at 7k. If good at 7K, have it checked at 9K, and so on. You will find out when a good average mileage will be once you are able to sort out the results.

We do an oil sample on every oil change in our diesel fleet. If we see a pattern develope, we change mileage/time accordingly to get the maximum, but safe, life out of our fluids and filters.

James