I don't see why you couldn't use them at the pump. Actually it is a useful bit of info. I normally don't buy at Esso, but they do have a promotion with Aeroplan for a bonus 250 miles if you spend more than $90 before July 29. Useful if the price is comparable to Costco.So you save around 5c per litre. I fillup at Costco which is still cheaper.
Question - can you use these GC's at the pump? Or do you have to redeem them inside at the cashier?