No issues with the engine to date. It's a 2010, so I like to think they had a good handle on making them by that point. I originally used the Castrol TWS, but having used Redline so extensively in racing vehicles, I thought I'd try it in this application. Anecdotally, the engine seemed to run better on it. I did a UOA that was inconclusive. I've always warmed up engines before really giving them the boot, the E63 is no exception. The F12 is faster producing more power, but it doesn't have the same visceral appeal to me. The howl of the S85 is inspiring. As for fuel economy, it does better than the Viper, but it has also been modified a bit. But it doesn't matter as neither is a 'daily driver', they are just for fun, and don't accumulate a lot of mileage annually.