My 19-year-old son and I drove from Virginia to Florida last week. The Boxster was stuffed, both trunks were completely full. I was pleased to get 28 mpg on the highway with the top down on our base 2000 car. We held the speed at a pretty constant 76mph. I cannt seem to force myself to drive through a tank of gas with the top up just to check the top-up mileage.
Ed