Free Fuel Log Book — No Sign-Up, Works Offline

How it works

Every time you fill up, enter your odometer reading, fuel added, and cost. The tool calculates your fuel efficiency automatically.

Only full-tank fill-ups are used for efficiency calculations, because partial fills don't give accurate MPG. The distance driven is the difference between consecutive odometer readings.

Frequently asked questions

Does this fuel log work offline?

Yes. All data is saved to your browser's IndexedDB storage, which persists across page reloads and works without an internet connection. Once the page has loaded, you can use it entirely offline — ideal for logging fill-ups in your garage or on the road where signal is weak. Note: clearing your browser's site data will erase entries, so use the CSV export as a periodic backup.

How is MPG calculated from odometer readings?

The tool uses the difference between your current odometer reading and the previous one to find the distance driven, then divides by the fuel added: MPG = (Odo_now − Odo_prev) ÷ Gallons. This is the standard fill-to-fill method used by most physical fuel log books and apps like Fuelly. Only entries marked "full tank" are used, because partial fills make the calculation inaccurate — the leftover fuel from a partial fill inflates the next MPG figure.

Can I track multiple cars or a fleet?

Yes. Use "Add Vehicle" to create a separate log for each car, truck, motorcycle, or RV. Each vehicle has its own unit system (US MPG, UK MPG, or L/100km) and independent history. You can switch between vehicles instantly and export each one separately as CSV or PDF.

What is a good MPG for a car?

For US vehicles in 2024, the EPA average across all cars and light trucks is about 28–30 MPG combined. Economy sedans and hybrids typically hit 35–55 MPG; trucks and SUVs often range from 15–25 MPG; and full hybrids (like the Prius) exceed 55 MPG. For UK MPG, multiply US MPG by about 1.20 (1 imperial gallon ≈ 1.20095 US gallons). In L/100km, lower is better — 6 L/100km is efficient, 10–12 is typical for an SUV.

My MPG seems lower than expected — what could cause it?

Common causes include: cold weather (engines use more fuel when cold), city driving vs. highway, tire under-inflation (adds rolling resistance), roof racks or cargo (aerodynamic drag), ethanol blends like E85 (about 20–25% lower energy density than pure gasoline), overdue air filter or spark plugs, and excessive idling. Tracking fill-ups over time in this log helps you spot sudden drops that could indicate a mechanical problem.

Is my data private? Does it go to any server?

Your data never leaves your device. There is no account system, no analytics, no upload. Everything is stored in IndexedDB inside your browser. The only time data leaves your device is when you choose to export a CSV or PDF — and you control where that file goes. This tool is fully client-side: you can inspect the page source to verify.