I keep track of all my odometer readings on all of my vehicles. I really had not given much thought to smaller diameter wheels when worn. That would explain why my 1995 Geo Tracker was slowly getting better MPG figures the more I drove it.
The log book I keep in every one of my vehicles is handy to see when the last brake job, tire replacement, oil change, or something else was done. I also thought I had an accurate MPG figure as I could add all the gallons and divide that into the total miles travelled.
Sample below - date, odometer, gallons, tank fill mpg, overall since purchased.
02/12/12 117,491 7.6 22.4 23.7
02/19/12 117,652 6.3 25.6 23.7
03/02/12 117,801 6.6 22.6 23.7
03/13/12 117,959 6.4 24.7 23.7
03/23/12 118,135 7.0 25.1 23.8
03/31/12 118,324 7.1 26.6 23.8
04/10/12 118,492 7.0 24.0 23.8
04/17/12 118,665 Oil Change 23.8
04/17/12 118,667 7.1 24.6 23.8
04/27/12 118,789 4.9 24.9 23.8
05/10/12 118,962 7.0 24.7 23.8
05/25/12 119,155 7.7 25.1 23.8
05/31/12 119,314 6.5 24.5 23.8
06/11/12 119,512 7.8 25.4 23.8
06/17/12 119,693 7.3 24.8 23.8
07/01/12 119,870 7.4 23.9 23.8
