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Cost per mile
The pump price tells you what a gallon costs. Cost per mile tells you what driving costs, and it's the number that actually compares vehicles.
The formula is one division: gas price ÷ MPG. A $3.00 gallon in a 30 MPG car costs 10 cents per mile. The same gallon in a 15 MPG truck costs 20 cents per mile, twice as much to go the same distance, at the same pump price.
That is why efficiency matters more than hunting for a station a dime cheaper: doubling MPG halves your cost per mile at any price. The table below shows the fuel-only cost per mile at illustrative example prices.
| Example price | 20 MPG | 30 MPG | 40 MPG | 50 MPG |
|---|---|---|---|---|
| $2.500/gal | $0.125/mi | $0.083/mi | $0.063/mi | $0.050/mi |
| $3.000/gal | $0.150/mi | $0.100/mi | $0.075/mi | $0.060/mi |
| $3.500/gal | $0.175/mi | $0.117/mi | $0.088/mi | $0.070/mi |
| $4.000/gal | $0.200/mi | $0.133/mi | $0.100/mi | $0.080/mi |
For your own numbers at the latest published national average, use the fuel cost calculator. Fuel is only part of ownership cost; maintenance, insurance, and depreciation are not included here.