How does Fuelio calculate cost per mile (or kilometer) in the fuel log?

Fuelio shows the cost of the fuel you actually used on that stretch, not the price of the fuel you have just bought.

The fuel you add at a fill-up is burned on the next drive. The fuel used on the drive since the last fill-up was bought at the last fill-up. So for each fill-up Fuelio takes the price per gallon from the previous fill-up, multiplies it by the fuel you add now (which is how much the car used on the way), and divides by the miles driven between the two.

Example

You filled up at 41,250 miles at $3.40 per gallon. At 41,562 miles you add 9.4 gallons at $3.60 per gallon.

• Using the new price: 9.4 × $3.60 = $33.84, and $33.84 ÷ 312 miles = 10.8 cents per mile.
• What Fuelio shows: 9.4 × $3.40 = $31.96, and $31.96 ÷ 312 miles = 10.2 cents per mile. The $3.60 fuel is counted on the next stretch.

The first fill-up has no cost per mile yet, because there is nothing before it.

Read more about the fuel log, also called the mileage log.