I have an Executive Business membership and a Citi Costco Visa.
Think if I buy diesel from Costco, get 2% off from Costco and 4% off from Citi Costco Visa (fuel) on top of the prices which are always cheaper than Safeway or QFC.
If I buy fuel anywhere else on my Costco Visa, still save 4%.
I gave my sister my +1 card so I also get 2% on everything she buys too, which is a lot.
Pays for the $120 membership and then some.
I keep sending her links to sales so she buys more stuff at Costco.
But if you work the Safeway/QFC rewards you can get up to a buck a gallon off.