Mine's regularly, though infrequently, popped up that message ever since I've had the car. Did you put different gas in it? I'm 99% sure mine's related to the anti-knock rating of the gas I put in. After someone posted a link to that gas quality website, I started filling up at the nearest place on the list and didn't get the message again until I put in the half tank of 89 before I put in the 93 (they don't sell 91, so I mix 93 with 89). So long as I put the 93 in first it's fine. I think people have posted before just how sensitive the V8 is to what it's fed from the petrol tank. I'm reluctant to run it just on 93, partly because of cost, but mostly because of the hotter combustion and the potential effect it might have on the valves.