Gas
I'm talking from experience. I owned a 99 BMW 540. Manual says premium. I was cheap ans started putting in 87. After a my second fill up the car started to act up. It was not bad gas because i bought regular gas for other vehicles i owned from that gas station and had no problems. Ended up having to drain the tank and put in 93. Car started to run like a champ in less than a week. Run the gas that the manufacturer says.



The argument still stands though - $300 in gas vs those outlined parts costs still makes the point.
and I agree
