Silly is as silly does.
I like math.
Post 1 - 17.5 mpg
Post 2 - N/A
Post 3 - 12 mpg
Post 4 - 18 mpg
Post 5 - 10 mpg
Post 6 - 15 mpg
Post 7 - n/a
Post 8 - 13.5 mpg
Post 9 - 15.5 mpg
Post 10 - 15 mpg
Post 11 - N/A
Post 12 - 13 mpg
Post 13 - N/A
Post 14 - N/A
Post 15 - N/A

Based on 20 gallon tank because I like easy math.

Overall average - 14.4 mpg