It was a blistering 60 Degrees F outside (in Colorado) so I had to turn on the A/C. Didn't notice any difference in gas mileage or engine revving but I was on the highway. Since this will be my first Summer with a Bimmer, I was wondering if you veterans noticed any effects on the vehicle when driving with the A/C on. Did the gas mileage suffer dramatically and is degraded performance noticeable in city driving?