91 vs 89 Octane for 2011 BMW 535i engine

The real problem I have is that a person who was more than willing to shell out the money for a $50k+ car suddenly can’t open his wallet enough to put the required fuel into his gas tank every fill up.

Things like this make me wonder if he’s even using the proper BMW spec oil for the engine, and changing it at appropriate mileage intervals in his $50k+ car. Heck, does he even pop the hood, and check the oil level every couple tanks of gas, or is it running several quarts low right now, on incorrect oil, at a way longer oil change interval than non-spec oil should ever be used in this engine?

I feel sorry for the next owner who buys this car after the OP returns it after his lease ends, or when he wants to upgrade to the next bigger/better BMW they sell him in a couple of years.

I know I wouldn’t want to be the next guy to own that car.

BC.