First, if anyone knows where to find cheap gas, please let us know. We could use a break from paying close to, or more than, $4 a gallon.
As far as the pump price affecting engine performance or gas mileage, we doubt there is a direct correlation. In fact, the off-brand station that sells for less than the name brands may be pumping gas made by one of the name brands.
That dirty little secret of the retail gasoline business became public knowledge in August 2012 in the Chicago area, northwest Indiana and southern Wisconsin, when oil giant BP recalled more than 2 million gallons of gas contaminated with gunk that was causing cars to run poorly or stall. BP said at the time that most of the gas was delivered to its own stations, but some also was delivered to other brands, found here. Among the other brands were Phillips 66, Speedway and Citgo, as well as retailers such as Meijer, Sam's Club, Road Ranger and Thorntons.
Like other refiners, BP claims its gas is better than the others, but the convenience store across the street might be selling the same stuff, just at a lower price.
The price at the pump is, of course, based on wholesale prices, but it's also partly a result of marketing strategy and a pricing decision by the owner/operator of the station. Major brands that traditionally charge more, such as BP, do so because they spend millions on advertising to convince consumers that their gas is better. To us, all gas is about the same, and no company has a secret formula that gives it superior quality.
If you experience poor performance or other problems after filling up, it could be due to contamination at the refinery, which was the case with BP. More likely, it could be because the storage tank at the gas station is contaminated with dirt or water, and when you pumped gas, it was nearly empty so you pumped out the water or crud that was near the bottom.
If you track your fuel economy, try different brands and give each two or three fill-ups to see if there is a noticeable difference that can't be explained by weather or unusual driving patterns. You might find that the cheaper brand is just as good.