Sort of OT, but may help someone.
I fill up every Saturday. I got this Mobil Speedpass thing, it's a transponder you use at the pump, and you can attach it to any credit card you want to (I have a card I use that I get points on, just a normal Master Card or Visa).
Anyways, with the Mobil speedpass, on Saturday Mobil takes off 6 cents a gallon, has been a promo they have had for quite a while I guess, I just found out about it last summer so I gas up my truck and my wifes car every Saturday now.
http://www.exxon.com/speedpass
Doesn't cost anything to get it either. If you link it to a Mobil credit card I guess you can save even more.