Excellent plot.
Yes, I also wish to play with the raw data in .xls or .csv format. Also, what kind of tires do you have? What I really want to know is your CdA and CRR. Also, what's the total amount of distance covered and fuel used in the trip? It would be good to compare measurements from your odometer to your datalogger.
Btw, you can also calculate the amount of fuel you'd save with a kill switch.
Yep, this is worth firing up MATLAB for.