How is the estimated fuel cost calculated, and what happens when fuel prices change?

Estimated fuel cost is distance ÷ the car's fuel economy × its fuel's price, using the values in effect on each trip's date. It only appears once the car has a fuel economy and its fuel has a price; trips without both are left out and the report says so. A fuel's price is shared by every car that uses that fuel. When you change a price or a car's fuel economy, choose From a Date to apply it from that day forward (earlier trips keep the old value) or Fix Current Value to correct a mistake, which also updates the past trips that used it. Each fuel and car keeps a history; long-press an entry to delete it. The amount is only an estimate. If you're reimbursed, the actual amount is calculated by whoever reimburses you.