If a gas station brand advertises Top Tier(tm) gasoline at all, every location must supply it. Diesel is location dependent and warrants more consideration.
All fuel sold at Costco is Top Tier.
I generally buy my gas at Kroger. I do buy premium as my car requires it. In some quick research just now I discovered that Shell is a major supplier of gas sold by Kroger, which bums me out as I have a long-standing personal boycott of Shell products.
What's your beef with Shell products?
BTW thanks for the post on Kroger: they've been tempting me with credit card offerings (lower gas prices and food discounts) recently and your post pushed their attempts into focus. Now I have a new quandary: Costco vs Kroger?