TLDR: less traffic near opening and closing; often long waits; gas delivery around 7pm; members only
Costco has provides its members with additional savings at the pump! I love the fact that you can use a gift card (without a membership card), any debit/ATM card, or an American Express as a form of payment.
I often come around 7 am or 9pm to avoid the long lines and the heat. I've read somewhere that prices are better toward the latter portion of the work week so I attempt to frequent on a Thursday or Friday. I appreciate how the fuel exceeds the EPA detergent requirement by at least five times so I hope it does my car good.
The attendant is generally friendly and I even have seen him swipe a member in if absolutely necessary. Kudos on the service!