My C5 came with mobil one right from the factory. Had a sticker by the fill tube to only use mobil one. I changed oil every 5k miles and the car ran great and the oil never looked dirty or smelled foul when I changed it.

I'm switching on my first oil change.

 

1) if want to switch back, go with Mobil1 DriveClean. It's totally compatible and its a high detergent mineral oil. And its known to keep a VQ35 happy (blackstone tests on maxima.org).

2) The Corvette and 911 dont have a VQ35, so it doesnt matter what they come with from the factory. There is more than enough information floating around that shows that the VQ isnt broken in until 5K. Youre not making the most HP until 5K, or the best gas mileage.. Why prolong that by going to syn? Even if you discount the ring seating issues, a little patience will pay off. I find that odd, you care enough to use syn, but not worried about the VQ being broken in fully? I think your heart is in the right place tho.. Just dont assume everything that applies to other engines also applies to the VQ. Same with Honda and Toyota motors. They all have their own unique quirks and care. (like sludging issue, a slightly thinner water jacket and you totally change the conventional wisdom about oil)

 

You should use Synthetic and then get a lab test done by Blackstone and you'd change your tune

 

well, that depends.. I have 80% city driving and Blackstone reports dictate a 4000 ODI for me (with Mobil1). The oil is fine and could probably go another 4K, but I hit the wear averages sooner with all the short trips and running rich all the time.

From what I've read, over 7000 has some mixed results.. Not saying it cant be done, just not by everyone and their specific driving condtions.