I have a 2013 Infiniti G37x with 41,000 miles on it, bought it recently. I just had an oil change with Valvoline SynPower synthetic. My car is kept in a garage. I do not drive very much, maybe 3,000 miles a year It's 80% stop-and-go city driving, trips of 15 to 30 minutes. So a ~7,000 mile oil change interval would be over two years. I I think that that would be too long, all the anti-corrosion and acid-neutralizing additives would be used up, though the oil's lubricating properties might still be OK. MY QUESTIONS: 1. How long a TIME interval is appropriate? 6 months? 9? 12? I don't want to cheap out, but I don't want overkill either.... 2. Do synthetic oils have more anti-corrosion additives than dinosaur oil?