Normally I just pay for everything using my cashback credit card and am fine with that.
However if I buy gift cards at my grocery store, I can earn more fuel points (=cheaper gas)
I have gift card that gives me 5% cash back when I use it.
so I use the cashback credit card to put money on the 5% gift card that I can use to buy other gift cards to earn more fuel points.
Confusing, I know. But it is saving me money.