I carry "frequent shopper" cards from Winn Dixie, Kroger, Tops, City Market/Smiths and a couple of others. Some of them have stores only out west or in NY/PA or some such that I may only visit every two or three years.
But.....when I AM there I use the card generated discount on fuel purchases whenever I find diesel (which is frequently). I have fueled at grocery store gas stations with the 35' fiver on. Not easy, but possible. (I DO try to do it after we have dropped the trailer for the night as this causes much less aggravation for other drivers.)