Enter the fuel economy of two vehicles, an annual mileage and a fuel price, and get each vehicle annual fuel use and cost, plus the difference per year and over five years.
Annual fuel use is annual miles divided by the MPG figure, and annual cost is that fuel volume multiplied by the price per gallon. When litres per 100 km is selected, the figures are first converted to US MPG by dividing 235.215 by the L/100 km value. The comparison is an estimate based on the figures entered: official economy ratings are measured on test cycles, and real consumption depends on driving pattern, speed, load and weather, so two vehicles compared here keep the same relative gap only if both are used the same way. Fuel price is assumed constant over the five-year view.
How much does a few MPG actually save? Less at high MPG than at low MPG, because fuel use is miles divided by MPG. Going from 15 to 20 MPG over 12,000 miles saves about 200 gallons a year; going from 35 to 40 MPG saves only about 43 gallons at the same mileage.
Can L/100 km figures be compared here? Yes. Select litres per 100 km and enter both vehicles in that unit; the tool converts each to US MPG (235.215 divided by the L/100 km figure) and then works in gallons, miles and the price per gallon entered.
Why might real savings differ from this estimate? The estimate holds mileage and fuel price constant and takes the economy figures at face value. Real economy varies with journey type and conditions, and prices change, so treat the five-year figure as a planning estimate rather than a promise.