Using the car’s calculated mpg reading is an estimation and does not tell you accurately about the long term mpg. Using just one or 2 fill ups and manually calculating the mpg can lead to errors due to fill ups. But keeping a records of fill ups in an excel spreadsheet can give a more accurate long term views and the errors tend to equalize out.
Here is one that I have created.
Remember
- I am in the medical field and not in accounting and have only limited knowledge of Excel. If someone can modify it to make it more efficient you may.
- All you need for the records are the small tear away print outs that you get when you fill at the pump using your credit card. It contains all the information except the odometer reading. It would be nice to record it each time but it does not matter since only the last odometer reading is needed for calculation of overall mpg.
- The last odometer reading divided by the gallons filled just before the current fill up gives an accurate mpg. In my spreadsheet the value of 26.98 mpg is inaccurate since it shows the 14 gallons filled on 10/14 but does not show the miles obtained from it. Either I should wait for the next odometer reading before the next fill up or remove the 14.00 gallons to show the last accurate mpg of 34.59 mpg.
- The cost per gallon is the total amount paid divided by the total gallons filled.
- You can insert rows above the last column in order to increase spaces to add data should 29 fill ups readings not be sufficient.
- I have 2 gps usb receivers and 2 software programs and both show a 4 % error in the speed. ie. 70 mph on odometer is truly only 67 mph. Both my Accord and Odyssey are spot on the gps readings. But I have yet to do a “gps trail” calculation if the odometer reading is also inaccurate. I will let you know after I do a decent sized trip to see its error margin.