Costco regular gasoline costs $5.87 in California near Disneyland today. According to what I read a few years ago, each Costco store determines the lowest fuel price among the five nearest competing gas stations, and then they match or beat that price.
I was on a trip to N East AZ about 590 miles we were trying make it a full round trip on 1 tank of gas in my RAM 3500 6.7 turbo. But ran shirt so topped of a Williams AZ at 6.29 so it took 2 times to fill it as the pump shuts off at 100.00 and even 2 tries left me a bit short of full.
Topped off yesterday just to beat the next increase. Here in Payson AZ it was $4.79 yesterday (6/18) at Maverick - the Speedway stations were the same price.