Ok, here's another way to bring the cost down, but it's complicated and won't work for all. For me I could get $1 off of gas, up to 35 gallons, so 35 additional savings.
To make this work in a minimal way...
You'll need a store that gives fuel points for purchases, and that has a gas station close to you. For me this is Kroger (Grocery). I googled "fuelperks" and there are many other stores (BiLo, Martins, WinnDixie, Giant Eagle, Fred Meyers.... etc). Three of my local Kroger grocery stores have fuel centers. If yours don't, you might find a shell station that accepts fuel perk points. My closest shell station does ... but many don't.
You need to be part of the loyalty program within the store. For me, Kroger. This automatically makes you a member of the fuel perks program.
They need to sell HD gift cards (most do).
Buy a gift card to cover the cost/partial cost of the combo. Use the fuel points before they expire. Don't let this confuse you, the HD gift cards never expire, but the fuel perks points do.
To further maximize savings:
Buy the most gas you can and that your fuel program allows and do it during a single visit to the pump. For Kroger members that's 35 gallons. With my kids home for the summer (5 us in house, 4 drivers, 4 cars plus my truck ... it's easy. I also have several gas cans for yard tools and my generator. Wait for several cars/cans to be near empty. What I'm saying is that if you only fill up with 15 gallons, you won't be allowed to use those points later, they only are available during one use of that pump.
If the store gives more points per dollar purchased on gift cards you'll save even more. For me, Kroger currently gives 2x the points. Rarely they give 4x the points, but only for a short while and I never know when.
Here's the math on my easiest example just buying 500 in gift cards.
They double the points, so I have 1000 points so that's 35 dollars savings.
Drive to the Kroger station together, get in line at a single pump. Use your loyalty card at the pump, and don't hang up the pump until you have pumped 35 gallons. I usually drive 2 cars and park on opposite sides of a single pump and just pass the nozzle from car one to car 2. Sometimes I bring a very thirsty car and several gas cans .... you get the idea.