Roof Box Impact On Fuel Economy

The empty roof rack had a nearly 2 percent impact on fuel economy which translates to a little more than three quarters of a gallon of gas.

Roof box impact on fuel economy.

Aug 2 2010 3 20pm 0 0. Not all down to the box some would be due to four people in the car and the boot full as well. Roof boxes too are designed to be wind cheating so at low speed their impact on economy is negligible. The control test the tourx without roof rails installed revealed that adding roof rails alone decreased the car s fuel economy by about seven percent or a negative 2 mpg change.

A large blunt roof top cargo box for example can reduce fuel economy by around 2 to 8 in city driving 6 to 17 on the highway and 10 to 25 at interstate speeds 65 mph to 75 mph. But the higher the speed the more affect they have. Rear mount cargo boxes or trays reduce fuel economy by much less only 1 or 2 in city driving and 1 to 5 on the highway. They found that in 2015 roof racks nationwide were responsible for 0 8 percent of light duty vehicle fuel consumption or 100 million gallons of gasoline.

Adding a roof box means your car has to carve a bigger hole in the air which requires burning more fuel so your mpg will suffer. All my thule stuff was one of my best purchases in a while browsed cl and got all my stuff for about 150 bucks would have been 350 400 new. My jetta wagon goes from 29 5with nothing on the roof to 27 5 with a box. According to used car buying guide parkers extra weight can reduce a car s mpg by up to 20 per cent because the engine has to work harder to haul it around.

Their study was published recently in the. 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. 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. Check the instructions about maximum speed mine states 60mph max it has seen 90 but i did get nervous.

Mileage went from 41 mpg at 65 mph to 40 mpg. But no matter how aerodynamic it might look it also alters the flow of air around your carefully shaped wind tunnel tested.