A long drive makes fuel price differences obvious in a way that daily commuting does not. Cross a state line and the number on the sign can move sharply, for reasons that have little to do with the station itself.
State fuel taxes are the largest visible difference
Every state levies its own tax on motor fuel, on top of the federal one, and those rates differ substantially. The tax is included in the posted price rather than added at the register.
States set these rates through their own legislatures for their own road funding needs, and some adjust them on a formula tied to fuel prices or inflation. Rates are revised periodically, so any figure ages quickly.
This is why price maps often show a visible seam along a border, with stations clustered on the cheaper side.
Not all gasoline sold in the country is the same product
Some regions require reformulated or seasonally adjusted blends to meet air quality rules, particularly around large metropolitan areas. A refinery has to produce that specific blend for that specific market.
A specialty blend has a smaller pool of suppliers, which makes its price more sensitive to any refinery outage or pipeline problem. Ordinary supply hiccups therefore hit those markets harder.
Blends also change between summer and winter for volatility reasons, and the changeover period tends to be when prices move most.
Distance from the pipeline shows up at the pump
Fuel moves cheaply by pipeline and expensively by truck. A station near a distribution terminal has a shorter and cheaper final leg than one in a remote county reached only by road.
Mountain corridors, island communities and sparsely populated stretches all pay for that last leg. The cost is small per gallon but consistent, and it compounds with low sales volume.
A station selling modest volume also has to cover its fixed costs across fewer gallons, which lifts the margin it needs.
Competition on a corridor sets the local floor
Where several stations sit within sight of each other, prices converge downward because drivers can compare without leaving the road. A lone station at a junction has no such pressure.
Interstate exits with a single operator, and stations positioned where the next fuel is far away, price accordingly. That is a location premium rather than a supply cost.
Why chasing the cheapest sign rarely pays
Detouring for a lower price consumes fuel and time, and on a typical tank the saving is measured in a few dollars. The arithmetic favors filling where you already are.
The useful version of this knowledge is directional: top off before entering a high-tax or remote stretch, and do not bother optimizing within a single metro area.