Haven't put anything but 93 octane in all my BMWs since 2001. All BMWs have the same fuel requirement, and the "minimum 89" means you can't run "regular" gas, but 89 will be ok in an emergency situation when 91 or 93 isn't available. The difference in cost for a fill-up will be about what you pay for one of those mocha-choca-lava-java coffees at Starbucks.
