Big news for me: my average mpg for the life of my Fit (that is including every single fill up and every single mile driven accept for the two tanks I missed because my wife filled up and didn't write down the mileage) is now just over 40 mpg: that's 40.03156 mpg for the life of my Fit (a little more than 15,000 miles).
And now on to the new update for the latest fill-ups:
Gallons Miles Tank's MPG
10.081 436.20 43.26952
8.756 371.20 42.39379
9.305 407.90 43.83664
9.213 401.20 43.54716
9.214 407.30 44.20447
8.537 387.50 45.39066
That's 23 straight 40+ mpg tanks in a row now.
In general I filled up one click past the shut off, used no A/C, did a bit of drafting, kept my speed under 60 mpg, but over 55 mpg, some coasting downhill with the engine off, shut off the engine, coasted up and waited at long traffic lights and have my tires inflated to the pressure listed on the side of the door (I might try five or ten percent over that some time in the future).
Just adding up the total gallons and miles gives: 355.5320 gallons over 14232.50 equals 40.03156 miles per gallon.
Finding the mean mpg of the fillups listed above gives 39.99797 mpg with an error on the mean of 0.5636812.
Either way it looks like the lifetime average for my Fit is 40.0+-0.6 mpg.
My CleanMPG chart keeps looking nicer all the time:
Fitting the mpg as a function of the number of days (x) I've owned the Fit to
mpg = a*(1.0-b*exp(c*x))
gives an estimate the maximum mpg (a in the above equation) of my Fit (the mpg as x tends towards infinity) driven on my commut. Based on the mpg data I've recorded the fit gives a limiting mpg of 46+-2 with a chisquare of 1.1. This is lower than some of the mpg reported on this site, but perhaps that's due to the amount of hills I drive on my daily commute (shown in this
post).
One thing I did note was that when I filled up with the highest octane possible (on accident, I wasn't paying close enough attention to the buttons when I pushed them) I saw a 2.7% increase in my mpg for that tank. Unfortunately, the price of the high octane was 5.2% higher than the lowest octane (which I usually use). Given the 5.2% greater cost of the higher octane case, the 2.7% increase in mpg (if it was really due to the higher octane gas) seems moot when one looks at miles per dollar.