The city driving I have been doing for the past few months has been horrendous - lots of road work being done in town and long waits, etc. SOME use of air conditioning, but also used it when I was getting great mileage on the highway. No more, nor less. I am, for various reasons, filling up when I am still about half full (yesterday was because I am going away for a few days and leaving my car with someone who is getting up at 5 am to drive me to the airport and I don't want her to feel that she has to pay for gas!), but I don't think that would make any difference. I also didn't fill it myself yesterday, but don't know if that would make much difference.