Hey roof rack people...how much did your MPG suffer?

Back in '07 we did a 7500 mile trip with our '04-- two adults, two early teens, all the camping gear, including some in dry bags on the roof tucked between bike rails on the roof rack with spoiler on front. We committed to driving 60 mph and averaged 50 mpg for the trip, which was 3 under our lifetime average for that car. Your choices may vary!

 

That's unbelievable, I can't even get 50mpg without a roof rack