Any claim for a 20% boost in MPG is always going to look dodgy!
For years aircraft have had micro-drilled holes in wing surfaces, which (if I remember correctly) create tiny pockets of low pressure when an airflow moves over the wing surface. The low pressure helps keep the airflow attached to the wing surface, albeit for the purposes of generating lift rather than reducing drag, but hey I guess it can work both ways. Fans of The Simpsons may remember Homer pickaxe'ing "speed holes" into his car, although they were slightly bigger than a fraction of a millimetre...
Any aero experts out there feel free to point out the bits I got wrong!
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Anthony
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