If you want a few tips on how to possible save a few bucks when you’re filling up, keep the following points in mind:
Never fill-up when the refuelling tanker is at the station. Firstly, the process of pumping the fuel underground adds oxygen to the fuel, so as you pump it, you end up with less once it settles in your tank. Of course you are also getting particles of the stirred up crap from the underground reservoirs in your car tank as well.
Try to fill up early in the morning, or late at night. This is typically when the underground reservoirs are cooler, therefore the fuel in its densest state. Therefore you get more actual fuel in your car tank. If you notice that you’re getting more or less mileage out of your car dependent on which station you go to, you can bet that the station which gives you less mileage heats their underground reservoirs. This expands the fuel particles, and therefore you get less actual fuel in your tank once it settles.
Give it a go, and you might notice a difference. I tested this theory again the other day when I was in a rush, and filled up at a station which had the refuelling truck loading up their reservoirs. I got about 80 km less that week.