The place where I buy groceries does the rewards perks too. Of course, I would like the spend have spent $100 for each 5 cents off per gallon. That is unless I spend my money at the grocery store on Tuesday when I get triple perks and only need to spend $33 for each 5 cents off per gallon.
IOW... That $1 off per gallon is already paid for.
I am a sams club member but have never gotten gas there. Their cash back is similar I suppose but I spend enough there to justify the $100 business rewards membership.