If you carried a Delta Branded American Express Card (ex. Delta Skymiles American Express), you can enrolled in Double (2x) Miles on your Gas and Groceries. The double mileage offer is valid from August 1, 2009 to December 31, 2009 for gas and groceries.
To enroll online, you must enter your Amex card number or log into “My Card Accounts” (MYCA) from the enrollment page. If you prefer to enroll by phone, please call 1-800-794-1308 and enter code 148790001. You can earn double miles at U.S. stand alone gas stations and supermarkets only if the merchant submits the charge for your purchase under the appropriate merchant code, industry code, or required service or product identifier established by American Express and the merchant.