I have been racking my brain to figure out how to get the maximum benefit out of my Costco membership, and still get AAdvantage miles via my AAdvantage Mastercard. As any Costco member knows, it's cash, debit card, check, or AMEX at the checkout. If you don't have an AMEX linked to the AA program, you were out of luck to get miles for purchases there.

I finally figured out how.

After financing my new truck via Costco.com's auto financing partern (I checked everywhere, it was the lowest rate I could get from banks, credit unions, on-line, etc...), I was sent a $20 Costco cash card as part of a promotion.

I went to Costco.com to see if I could recharge the cash card online, and they no longer offer that service online -- BUT -- I could buy another cash card at any value up to $2,000 and pay with my AAdvantage Mastercard. They ship the card to you via UPS for a nominal shipping fee (which also earns you miles), and then you have your Costco cash card to use the next time you go to Costco, and you get AAdvantage miles to boot!

If you're a Costco Executive Club Member, and provide your number when purchasing your Cash cards, you also will get your 2% cash back on the purchase of the card, and then 2% when you actually go to Costco to buy your items...so it becomes 4% cash back on top of the miles.