Another vote for UT with rental car savings. The car rental states up to 50% off, my next rental is 81% off as I am picking it up in Tampa and dropping it off in Daytona Beach with no extra charge(economy full week $185) in March.
With that said, the Kroger fuel/credit card rewards combo has been used many times, we've done the Meijer mperks $50 back on a $500 gift card charging on a rewards card for additional points. We've done the Sam's black Friday $500 for $449 before.