The avg numbers, for any period, of any stats, are being generated via a miles / gallons formula. When we generate these averages we ignore all fuelups that don't have a MPG or don't have a miles value stored. A fuelup might not have a MPG for several reasons, you marked it partial, you marked the previous partial, you put in an excessive number of miles, say 5,000.
So when I ask the database to tell me your numbers, I get 18,200.20 miles and 1,351.437 gallons. If you figure that out, you will get 13.36 which is where the 13.4 average comes from.
What numbers did you use to arrive at 14.1?
The numbers shown in the "Total Miles Tracked" and "Total Gallons Fueled" mini stats will differ from these numbers as those are displaying the total distance and miles, regardless of the mpg status of the fuelups.
These are SUM(miles_last_fuelup) and SUM(amount) versus the formula used for averages, which is along the lines of SUM(miles_last_fuelup) and SUM(amount) WHERE mpg > 0 and miles_last_fuelup > 0
The only number that is an avg of avgs is the Running AVG displayed on the dashboard. I need to change the data structure of the stored last 10 fuelups to resolve that one.
See my test car:
http://www.fuelly.com/car/acura/mdx/2009/freddie/298667
It illustrates what I am saying.
Miles / Gallons = 19.8 MPG
Sum of Avgs / 4 = 17.3 MPG
est73 
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