My husband and I are a lot alike when it comes to saving money. This is one of his ideas. The one gas station that we drive by on our way to town (30 miles) is a BP station. This is the most convenient gas station for us to use, no matter what you think about BP. ;) You can see on the above receipt (that is kind of cut off on one side) that 20 gallons cost $2.18. My husband paid extra for non-ethanol gas, which we use because it gives us better gas mileage and we like the idea of non-ethanol better.
BP has a rewards card that we have. They have changed the rules a number of times and the deal isn't quite as good now, but still worth doing. BP is banking that you will both buy their gas and possibly get behind on paying off your card and pay interest as well. The goal is to always pay the card off at the end of the month so you both get your rewards and don't pay any interest.
Here's how it works. You get 1% cash back on any purchase (used to be 5% on gas if I remember all this correctly). So, we use this card for lots of purchases including groceries, hardware or anything else we need. (We also have an airline miles card we do the same with). But we always, always pay it off at the end of the month before any extra is due. Then, after a certain amount of time, we get up to 20 gallons of gas. The trick here is that if you use, say 10 gallons of your rewards, you forfeit the other 10. You only get one reward. So, every time we get the reward my husband makes sure to use the reward in his pickup truck and he brings a large gas can as well to get all the 20 gallons of gas. They will also offer you the reward early and ask you,"would you like to get this tank of gas for $2.19 a gallon?" and we always say no because we want 20 gallons for free or practically free.
So I don't know all the minute details of this since this one is my husband's frugal tip. He saved me this receipt so I could put it in my blog. :) But here is the BP rewards program for you to read up on yourself. You can also do similar things at other gas stations and with other credit cards. But be sure to pay it off every month or it probably won't be in your best interest to do this.