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I like your method.
Plus, using a Honda Insight with its high mpg capabilities, expands the scale of resolution to see and discern subtle differences more easily.
Are you going to try testing smooth wheel coverings too ? They will most likely fall below your 2% threshold but, they might move the needle enough to gain a little Insight. (pun intended
)
Looking forward to your results as you test the various aspects of automotive aerodynamics.
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