Aerodynamics play a big part in a vehicles fuel economy. Witness all the newer big rig trucks with their aero rounded fenders and flarings and such. With that being said, what sort of aero tricks, both practical and unpractical, could we apply to our cars and trucks to make them more slippery. Just for fun. I will start with the tailgate up/down debate. I read a report that there is such a small difference it is not worth trying. I verified that once with my little truck and a scanguage. But a bed cover is supposed to decrease wind resistance. Did not verify that. Any other tricks?