"no additional discount but get the Gas Buddy app and save yourself from running around to check gas prices".
Another good one is Gas Guru. I set mine to "map" display and choose a fuel stop on or near my daily route. I usually save 25-30 cents a gallon for a few moments of research. GG works great for trips too. I plan my fuel stops by checking prices along my route and stop accordingly at lower price areas even if my tank isn't empty. I also fill up on Monday as that is almost always the lowest price day.
The Costco near me usually has near the lowest price around but there are other stations that meet or beat their price.
https://play.google.com/store/apps/details?id=com.yellowpages.android.gas
