PenFed has different cards. I use the Cash Rewards Visa Platinum for the 5% cash back on fuel every month. You can pay $25/year for the card or open a $25 money market account as we did. There may be other options. I asked about my dad being a veteran and that qualified.
We use Capitol One for all other Canadian purchases. No Canadian transaction fees on either of these cards unlike AmEx.
The PenFed card is the only one we use for any vehicle fuel purchase in the US or Canada except truck pumps. For truck pumps we pay inside with AmEx and get 5% cash back yearly at Pilot and Loves. We haven't recently purchased diesel at other truck pumps so they aren't listed.