I currently have 4 Pontiac Montanas in my taxi fleet, two 01's and two 03's. They are identical in terms of drivetrain, wheel base, useage, maintenance, and most optional items. The big difference I've noticed is that one of the 01's consistantly gets 2-3mpg better fuel mileage than the others. The only thing I can attribute that to is it's the only one without a roof rack. My question is, is it possible for a roof rack to make that big of a difference in mileage(~13%)? Has anyone tested this out? Or is this van just a factory freak? Because for 13% better fuel mileage, I'll tear all the racks off, seal the holes with silicone and toss them in the trash...lol!