Quick answer
A logbook records each fill-up, odometer reading, and gallons used, letting you calculate mpg over time and detect changes in efficiency.
Detailed answer
A physical or digital logbook helps drivers track fuel usage meticulously. Each fill-up, you note your odometer reading, gallons pumped, and possibly the station or cost. Dividing miles traveled by gallons gives you the mpg for that tank. Over weeks, you observe patterns—did new tires drop mpg, or did a recent tune-up help?
Some prefer apps on smartphones; others keep a small notebook in the glovebox. Fleets also rely on such logs for budgeting and maintenance scheduling. Either way, consistent records reveal your driving style’s effect and provide early warning if mpg suddenly slips, indicating mechanical problems like failing oxygen sensors or underinflated tires.
