Hmm, this is something I hadn't really considered. I will need to take a look at the OEM curve to see how it would affect my snowboard carriers.This is an older thread, but I thought it worth adding a point. The 2015 factory roof crossbars are curved. So, they are fine for some uses, but if you will haul lumber or sheetrock, you may want to look into a set of Thule or Yakima rails. They are about the same price as the factory cross bars, but are nice and flat. We keep the OEM rails on every day, to avoid a gas mileage hit, but switch to the Thule bars often.
What is the MPG you get with and without bars, both OEM and Thule? I am not surprised it makes a difference, but a little surprised that it makes a measurable one.