[aerohead]

I'm the nut-case who guestimated the Cd 0.116 requirement.
I'd be happy to revisit the calculations.
I do not have an accurate:
1) frontal area
2) all-up average travel weight
3) tire manufacturer
4) tire model
5) inflation pressure
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6) I was presuming zero hybrid function, just constant speed driving, only on the engine ( according to Emission Analytics, your hybrid system increases composite mpg by 48% because of regen ). It's impossible to calculate anything if the hybrid assist is affecting performance.
7) I'm driving a 2009 Prius right now. It's never indicated above 43.3-mpg on long highway travel, gentle rolling hills, @ 65-70, with AC 'ON.'
Thanks in advance for any additional data.