MPG differential at 4 years

[steven765]

So I now have 4 years of data on my baja.
I log every receipt, miles driven, cost and grade fuel. I'm going to start tracking average speed per tank thanks to the scanguage, but i digress.
Anyway so with that every year I add to the table the differential on MPG over the previous year. yada yada results

06 ave mpg 25.03
07 ave mpg 24.44
08 ave mpg 23.36
09 ave mpg 22.46

for a differential of -0.59, -1.08 and -0.9 respectively off the first year

and an average standard deviation of 1.75 for the years individually or 2.06 in total

I could run the linear regression for a pretty chart later, but it will just tell me what I can see: that I'm trending downward at about 1MPG/year .
Regretfully I wished I had ave speed/tank to factor that in.

For reference this is over 372 tanks of gas, 4550.4 gallons of gas or 109k miles. At the prices paid that's $12,567 paid out for gas!

-1Mpg/year is rather sad. I'm about the replace the oxygen sensors hopefully that restores it a bit.

Next up I need to calculate the average MPG by brand of gas.

Yes I'm bored, but this is me procrastinating from doing research
..back to work now argh