Roof Box Impact On Fuel Economy

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.

Roof box impact on fuel economy.

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. 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. 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. Not all down to the box some would be due to four people in the car and the boot full as well.

My jetta wagon goes from 29 5with nothing on the roof to 27 5 with a box. Roof box and fuel economy ijws15 used to lose about 4 5 mpg in the 1 8 t saloon. Aug 2 2010 3 20pm 0 0. 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.

But the higher the speed the more affect they have. 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. Roof boxes too are designed to be wind cheating so at low speed their impact on economy is negligible. 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.

But no matter how aerodynamic it might look it also alters the flow of air around your carefully shaped wind tunnel tested. 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. 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. It s impossible to give an exact figure because it depends on so many factors but britain s biggest roof box manufacturer thule states that your mpg is unlikely to decrease by more than 5.

Their study was published recently in the. Adding any roof box increases frontal area of your vehicle of course.