Two exits on the same highway can post fuel prices that differ by a wide margin. The fuel is identical, and the explanation lies in the economics of each site rather than in supply.
Highway sites carry different costs
Land beside an interchange is expensive, and the lease on a service plaza reflects that. Where a site sits on a controlled access road, the operator may pay a concession fee on every gallon sold.
Those sites also run longer hours and larger forecourts than a town station. Staffing a plaza around the clock and maintaining a dozen pumps is a heavier cost base to recover.
Delivery economics differ as well. A station that sells enormous volume takes full tanker loads efficiently, while an isolated site on a quiet stretch pays more per gallon delivered.
Captive demand supports a higher price
The strongest influence on a forecourt price is what the driver's alternative looks like. If the next station is a long way on, and the driver's tank is low, the site can price above the regional average.
Operators know this precisely because they can see where competitors sit. Pricing software works from distance to the nearest rival rather than from any notion of a fair margin.
The pattern reverses where stations cluster. Four forecourts visible from one interchange will price within pennies of each other, because a driver can switch by turning a wheel.
Fuel is often not the product
Margins on fuel are thin at high volume sites, and the money is made inside the building. Coffee, food and convenience goods carry far better margins than the pumps do.
That inverts the pricing logic at some locations. A site that expects most drivers to come inside will price fuel keenly to pull them off the highway.
Sites with no shop worth visiting have no such incentive. A bare forecourt with two pumps and a card reader recovers everything through the fuel price alone.
Taxes shift at invisible lines
Fuel taxation is often set at a regional or state level, and it changes at a border a driver cannot see. Two stations thirty minutes apart can sit under different tax regimes.
Local authorities sometimes add their own levy on top. A metropolitan area may tax fuel to fund transport projects, which raises the price across an entire urban zone.
Drivers reading this as price gouging are usually looking at policy. The gap follows administrative boundaries closely enough that it can be mapped.
Timing matters more than location
Wholesale prices move continually, but forecourt prices move in steps. A station that took delivery before a wholesale rise sells cheaply until that tank empties.
Prices also rise faster than they fall. Operators pass on increases quickly to protect margin and reduce them slowly, which widens the spread between neighbouring sites after a market swing.
The practical result is that a cheap exit stays cheap for a while. Drivers who note a good site on the outbound leg often find it still competitive on the way back.