As of this morning, gas prices for regular unleaded at the stations nearest to me were:
Costco 4.19
Chevron 5.19 & 5.09
Exxon 4.83
Arco 4.79 & 4.89
Valero 4.83
Shell 4.83
7-Eleven 4.79 & 4.49
Hope the formatting comes out OK ...
Those prices are very high, so I feel for you. I would also choose Costco, I assume you have to he or already are a member and that costs?
As to the Top Tier thing, I had heard they use Kirkland Signature gasoline, touted as having 12x more additives.. I would have a hard time believing that, that the cheapest (inexpensive) gas also has more additives that make it better than name brands. (Also, if that is no longer true, let us clarify that.)
But, as stated in another thread, even just today, I don't care if it is Top Tier or the worst of the worst Unbranded fuel, it moves so quickly you'll never have a problem with bad gas. Never.