Maybe a credit card that gives 5% cashback on gas purchases would be in the works? Also, when I've gone to Petrol Canada (I think that's the name... white background with the red maple leav?) in YUL and en route to YYZ, they've offered to sign me up for their reward program. Being US based and not there often, I didn't sign up for it, but it could be worth looking into.

As for US stations, I'm not aware of any national chains that have anything.