Car Fuel Efficiency Log
Log every fill-up and see your real mileage (km/L), fuel cost per kilometer, monthly projection and a mileage trend — saved in your browser.
Add a fill-up
Summary
Add at least two fill-ups with odometer readings to see mileage. The first fill-up sets the starting odometer and its mileage is not calculated.
Fill-up history
| Date | Odometer | Liters | Price/L | Amount | Mileage (km/L) | |
|---|---|---|---|---|---|---|
| No fill-ups logged yet. Add your first fill-up above. | ||||||
Mileage trend
Each point is one fill-up. Needs at least two fill-ups with calculated mileage to draw the trend.
How to use
- Enter the date, odometer reading in kilometers, liters added and price per liter, then click Add Fill-up. Always fill the tank full for accurate mileage.
- Mileage for each fill-up is computed from the kilometers driven since the previous fill-up, divided by the liters added now.
- Watch the summary cards and trend chart to spot drops in mileage that may mean low tire pressure or needed maintenance — keep a service record in the Car Maintenance Log.
- Your log is saved automatically in your browser. Use Clear log to remove everything.
Good to know
- Fuel type is optional and does not change the math — it is stored for your reference.
- The monthly projection scales your real average cost per kilometer to a 30-day month from your logged driving rate.
- Prefer miles per gallon? Convert any reading with the Fuel Consumption Converter.
- Everything is computed in your browser — no data is uploaded.
Frequently Asked Questions (FAQ)
How is mileage per fill-up calculated?
Mileage for a fill-up equals the kilometers driven since the previous fill-up divided by the liters added now. For example, if the odometer read 50,000 km at the last fill and 50,400 km at this fill, and you added 40 liters, the mileage is 400 divided by 40 = 10 km per liter.
Why is the first fill-up skipped in the mileage table?
The first logged fill-up has no previous odometer reading to compare against, so the distance driven before it is unknown and its mileage cannot be computed. It still counts toward total fuel spent, but mileage, best and worst are calculated from the second fill-up onward.
How is the cost per kilometer calculated?
Cost per kilometer equals the total fuel amount spent across all logged fill-ups divided by the total kilometers driven between the first and the last odometer reading. It tells you what each kilometer of driving costs in fuel.
Where is my fuel log data saved?
Everything you enter is saved in your browsers localStorage on your own device. No data is uploaded to any server. Deleting a row, clearing the log or clearing your browser data removes it permanently.
How does the projected monthly cost work?
The tool looks at the kilometers you drove between your first and last logged fill-up and how many days that covered, then estimates your monthly driving distance and multiplies it by your average cost per kilometer. It needs at least two fill-ups on different dates to project.