Two odometer readings and one receipt
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Questions
What is the formula for MPG?
Miles driven divided by gallons used. Miles driven is the current odometer reading minus the reading at your last fill-up; gallons used is what you just put in to fill the tank back up.
Why is my dashboard MPG different?
Dashboard readouts estimate fuel used from injector timing rather than measuring it, and they are commonly optimistic by a few percent. Two odometer readings and a pump receipt measure what actually happened.
Does this work if I only part-filled the tank?
Not on its own. A partial fill leaves an unknown amount in the tank, so carry the gallons forward and divide at the next full tank — that covers both fills at once.
Did your MPG suddenly drop?
If your calculated MPG is 3 to 5 MPG lower than your typical average, start with tire pressure and seasonal fuel blend before paying for diagnostic scans. Read our checklist on what to check when gas mileage drops, or scan for pending engine trouble codes in the OBD-II error code directory.
Never do pump arithmetic by hand again
Carvico is a private fuel and car expense log for iPhone. Snap a photo of your receipt at the pump — date, odometer, gallons, and cost are read straight off the paper, with true full-tank MPG calculated automatically. No ads, no trackers, and all records stay in your private iCloud.
Download on theApp Store