Yeah, it's a tough call. TONS of evidence that modern synthetic oils can easily go 15k - 16k kms between oil changes and still have plenty of oil left. Hasn't Ron actually sent some of his used oil out for testing, and that was the exact determination?
Then again, many engines in many vehicles are not tolerant of long interval changes (Ford 5.4L, I'm looking at you), and want their oil to be changed every 5000kms. It can cause real problems down the road otherwise.
For myself, I tend to put on 8000 - 9000kms on my vehicles per year, resulting in an annual oil change with an interval of 8000kms. That seems good enough to me. Although, I'm doing a lot of longer drives to go MTBing, so that may increase my mileage significantly, forcing me to do an oil change in the spring, rather than my annual one in the fall.
Also, Mazda recommends 8000km service intervals on the CX-5. Actually, just looking at their brochure, and Mazda recommends oil changes every 6 months, or 8000kms. Seems excessive. Whatever, I do every 8000kms, which ends up being annual. Full synthetic oil in my car.
