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Yes, if you don't mind the rewards being paid only annually, the TE is a very good card for a Costco member, especially one who buys a lot of gas at Costco (or anywhere else for that matter).
You might consider the Barclays Sallie Mae Mastercard for non-Costco gas purchases (5% on gas, 5% on groceries to a cap of $250 per month, 5% at bookstores and Amazon to a cap of $750 per month). But of course that's useless at Costco.