Quote Originally Posted by sweetwater View Post
The tailgate test usually works out to being an even trade off. You'll lose aerodynamic efficiency without a tailgate. The airflow creates a big area of low pressure behind the cab which creates extra drag. If you have a sliding glass window just open it with the tailgate down. However, if you remove the tailgate you gain fuel economy by reducing the weight of the truck. It seems reasonable to assume that without a cover you would reduce the aerodynamic profile of the boat thereby increasing mileage. With the cover on you protect the boat from debis and theives a little better. I'd just do whatever seemed the most important to me at the time.
The myth buster dudes did this test on their show one time.