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TEMP vs DRAG Estimator (winter / summer)
Hello all.
zjrog was lamenting mpg loss at another forum.At minus 19-degrees his Jeep is getting slammed at the pump.
I put this chart together as a quick reference guide to allow anyone to anticipate how drag might be influenced by changing air temps.
I've attempted to make it self-explanatory.Ambient temps are listed at the bottom.Locate your current temp,go straight up until you intersect the curve,and read your new air density directly to the left.(You can use linear interpolation to arrive at values that fall between values listed)
Divide this value of rho by the SAE standard 0.002377 to get your multiplier and use this with your vehicles published or estimated Drag-Factor( CdA ) to get your "virtual" CdA at the different temp.
I've included an example using my T-100 @ - 20-degrees F.As HWY MPG varies as 50% of a drag change,the 17.795% drag increase would reduce HWY MPG almost 9%.
Factor in thicker viscosities of all the lubes,and increased rolling resistance of colder tires,and it's a triple-whammy.
For summer operation,you will notice that on a 100-degree day,you can pick up 3.5% mpg without doing a thing.
I apologize for the US Standard units,and necessary conversions for SI units.
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