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I haven't fired up MATLAB, but here's some quick figures from Excel.
Your time weighted average speed is 40kph. Your distance-weighted average, however, is 57kph, and your sqrt(distance-weighted average(Vē)), which is what the air sees, is 60kph. IOW, if my math is right, your speed profile results in the same total aero drag as a car that cruised the entire 5.7km at 60kph, even though your average speed was 50% lower. (YMMV)
Put another way, you had 2.25 times as much aero drag as you would have if you could have just cruised non-stop at the "average speed" figure the scangauge would read out. I hope everyone here would know enough not to try an aero calc based on "average speed", though.
I used the Excel expression [ =sum(IF(Fuel_rate<0.5,Fuel_rate,0))/sum(Fuel_rate) ] and determined that you spent 31% of your fuel idling! (YMMV, bigtime) I bet you'll think long and hard about a stick shift or a hybrid next time around, so you can install a kill switch.
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