MPG Comparison Calculator (Fuel Savings Between Two Cars)
Enter both cars’ mpg, how far you drive and the fuel price.
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MPG Comparison Calculator (Fuel Savings Between Two Cars) by TheCalcTools
How the MPG Comparison Calculator (Fuel Savings Between Two Cars) works
Fuel cost = miles ÷ mpg × price per gallon. Because fuel used is inversely proportional to mpg, going from 10 to 20 mpg saves far more than going from 40 to 50.
Gallons per 100 miles (the reciprocal of mpg) shows savings directly, which is why the US fuel economy label lists it.
The formula
Worked example
Using the default values shown in the calculator:
| Car A fuel economy (mpg) | 25 |
|---|---|
| Car B fuel economy (mpg) | 40 |
| Miles per year | 12000 |
| Fuel price per gallon | $3.5 |
| Extra price of the more efficient car | $3000 |
- At 12,000 miles and 3.50 a gallon: car A $1,680, car B $1,050.
- Car B saves $630 a year, paying back 3,000 in 4.8 years.
Result:
| Car A fuel per year | $1,680 |
|---|---|
| Car B fuel per year | $1,050 |
| Yearly saving | $630 |
| Payback of the extra price (years) | 4.8 |
| Fuel saved per year (gallons) | 180 |
Frequently asked questions
Is upgrading from 40 to 50 mpg worth much?
At 12,000 miles it saves only 60 gallons a year, much less than 25 to 35 mpg (about 137 gallons).
Sources and further reading
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