Does My Roof Rack Affect My Gas Mileage?

The Roof Rack MPG Experiment

He compared the gas mileage of his car at 54.7 mph (88 kph) with 1) no roof racks, 2) an empty roof rack, and 3) a mountain bike on the roof rack.

He found that compared to the baseline of no roof rack, the empty rack reduced his MPG by -12.7% and the roof rack with a bicycle reduced it by a whooping -27.3%. And since air resistance increases exponentially with speed, the difference would have been even bigger at 70 mph (many people drive at that speed).

While the methodology isn't 100% scientific, and every vehicle will be affected differently by a roof rack, it gives a good idea of how big a difference a roof rack (empty and full) can make.

So please, if you're not using it, take the roof rack off your car (and forward this tip to your family & friends)! It's such a simple trick, like inflating your tires properly, that could save millions of gallons of gas.

Via MetroMPG