[aerohead]

* Just for giggles, I ran a set of aerodynamic road load calculations for a Cd 0.247 Tesla Model S at top speed ( 155-mph ). In U.S. units.
* In one, I used whatever was in the computer to complete the string.
* In the other, I truncated the values throughout, to two significant figures, regardless of what the computer 'said.'
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* Between the two, the truncated figures resulted in a 6.5% deviation in power, 152.27- hp vs 162.2-hp actual.
* 'Truncated' drag coefficient = Cd 0.2309 vs Cd 0.247 actual ( delta- 16 counts)
* 'Truncated' per-mile energy: 732.9 Wh /mi vs 780.6 Wh / mi actual.
* With zero changes to the car, numerical truncation leads to an implied 16-count drag deficit.
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It appears that truncation leads to an uncertainty which exceeds the spectra of some aero. modifications we might choose to investigate.