I don't think it differs so much from big names vs. no names, but it usually depends a lot on the owner of the gas station. Some no-brand places have great gas and there some stations that are shell, exxon, etc., that do weird stuff to the gas to reduce their costs. So really depends a lot on the place itself and not necessarily the brand. The places that charge more usually do just because they can, not because their cost is more, the exception of course is when they are paying more for the property their station is on.