Wax and Air Flow

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Sep 19, 2008
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This might be a "dumb" question but is there any quantitative evidence/data to show that a vehicle that is well waxed has better air flow caharacteristics? Since the friction of running a cloth over the surface is reduced when compared to a "dirty, non-waxed" one, is air affected the same way? If so, is it significant enough to show any increase in mileage? Just curious.
 
Joined
Apr 30, 2003
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Ontario, Canada
Shear rate at the surface is so low that a chemical treatment should not have any effect. Painting it black might make the surface warmer in the sun, which should reduce friction a tiny bit, but increased a/c use would outweigh that. A rough surface in the right places might make a difference.
 
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If I remember my fluids correctly, even an order of magnitude difference in roughness has minimal effect on the Reynolds number (which tells you if your flow is laminar, turbulent or in transition to turbulent) at low velocities. Velocity however has a 1:1 effect on the Reynolds number so relative air speed moving over a car's surface would have much more effect on friction than roughness. Still, this is minor compared to the other aspects of the vehicle's overall drag coefficient which is mostly determined by it's shape and front profile.
 
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Sep 10, 2005
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Erie, PA
Only on a plane will be make a measurable difference, and even at that it will not really equate to much unless it is a supersonic. A nice clean polished skin will have less drag.
 

Boomer

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Sep 19, 2008
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But my speedometer only goes to 300! Reason I asked was this was a debate at the local gym, with some swearing it made a difference while others did not. Thanks for the answers. I go back well armed!
 
Joined
Jul 25, 2009
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Boston, MA
No difference, but its the same psychological effect as when you fill up a tank of gas or get an oil change (assuming a 3000mi/oci)
 
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