Gas Prices Along Interstate 15

Updated April 5, 2026 — Prices updated regularly from EIA data

Route • 5 states

About Interstate 15

Running 1,433 miles from San Diego, CA to Sweetgrass, MT, I-15 connects Southern California through the desert Southwest, Utah, and Montana. Gas prices along I-15 vary dramatically — cheap in Montana and Utah, but expensive in California.

Avg. Price Along Route
$3.64
Est. Trip Fuel Cost
$145
Price Range
$3.20–$4.51

Gas Prices at Each Stop

Fueling Tips for Interstate 15

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Frequently Asked Questions

Interstate 15 spans 1000 miles across multiple states. For a vehicle averaging 28 MPG highway, the fuel cost varies significantly depending on which states and price zones the route covers.
Interstate 15 passes through or near major cities where competitive fuel markets and warehouse clubs offer the best prices. Look for Costco, Sam's Club, or high-volume discount stations in each major metro along your route.
A 2-mile detour to save 20 cents per gallon on a 15-gallon fill-up saves $3. With a car getting 28 MPG, the detour uses 0.14 gallons. Detours above 3-4 miles for savings under 20 cents per gallon are generally not worthwhile.
The cheapest gas along Interstate 15 is generally found in Montana, where lower fuel taxes and proximity to refineries or pipelines keep prices down. Avoid fueling at highway-exit stations in California, where tourist premiums push prices 15-25 cents above the best nearby rates.
For a trip along Interstate 15, a vehicle averaging 25 MPG would use approximately 1 gallon per 25 miles. At current average prices along the route, budget approximately {perMileCost} cents per mile for fuel. Plan fill-ups in lower-price states whenever possible.

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