How the math works
Fuel used = distance ÷ mpg (US) or distance × L/100km ÷ 100 (metric). Cost = fuel used × price. For a 300-mile round trip at 30 mpg and $3.50/gal: 600 ÷ 30 = 20 gal → $70.00, about 11.7¢ per mile.
| mpg | Cost per 100 mi @ $3.50/gal |
|---|---|
| 15 | $23.33 |
| 25 | $14.00 |
| 35 | $10.00 |
| 45 | $7.78 |