Who has the highest mileage?

JARblue

Change to another synthetic? Shouldn't be a problem any time. However, the Nissan Ester is a quality oil, albeit expensive. If the $$$ isn't a problem, I wouldn't bother switching if I were you.

Change oil change interval (OCI)? Are you doing it every 5K miles or kms? If you're doing it every 5K miles and wanting to switch to 7500 kms, that is equivalent to ~4660 miles; you might as well stick to 5K miles. If you're doing it every 5K kms, then you could probably go a little longer. If you really want to know what OCI you should be using, then your best solution is to send in a sample of your oil to Blackstone for a used oil analysis (UOA). They will tell you how often you should be changing your oil based on the actual oil you use.

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