The fact that they've taken great pains to make that happen, while remaining not only a Top Tier gasoline but remaining in complete control of their additive package and the quality of their gas, makes me a raving fan.Mine is similar: Costco is always the first choice, with any Top Tier being my second choice. And Costco's spot at #1 has mostly to do with the fact that it's usually at least $0.30/gallon less than anywhere else.
They go to lengths no other vendor has. And I trust the Kirkland brand; their custom additive package is at the very least consistent across all their locations. And they have a great reputation for quality.
It certainly helps that they sell so much gas, it's pretty much guaranteed to be fresh. Who knows how long it's been since Billy Bob's Bait and Gas got a delivery of whatever the tank had left over that day.