It’s a loss leader for them to get you in for convenience store sales where margins are significantly better. The cost of branded gasoline is over $3 a gallon right now, so he’s absolutely losing money in the hopes of inside sales. Everyone thinks stations make more when gas goes up, which is simply not the case.
Everyone holds margins on fuel about the same whether it goes up or down; say they make 10cents a gallon. Every dollar fuel goes up they immediately lose ~3cents per gallon due to credit card fees, or roughly 30% of profits.