Roof Box Fuel Consumption

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.

Roof box fuel consumption.

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. I would guess a roofbox adds around 5 to fuel consumption although there are many factors at play especially if you if you sloiw down to 60 65 you may then even see a reduction in fuel compsumption. Last year on a run to paignton 900 round trip we got about 35mpg fully loaded roof box included. However with the roof box it was only capable of 32 5mpg 31 per cent less than its claimed economy via the government tests.

But no matter how aerodynamic it might look it also alters the flow of air around your carefully shaped wind tunnel tested. Adding any roof box increases frontal area of your vehicle of course. The biggest problem we had was parking. Why do they have such an effect.

Leaving engines aside for a moment two major elements affecting a car s economy are weight and aerodynamics. 6 0 l 100 km 39 mpg thus the cargo box on the roof increased fuel consumption by about 5 compared to the baseline. The gear with the most impact were the dual mountain bikes strapped to the roof which impacted the fuel economy by 31 percent or 9 mpg. Their study was published recently in the.

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. 5 6 l 100 km 42 mpg roof rack with thule dynamic 800 aerodynamic cargo box. Roof boxes reduce mpg. 5 9 l 100 km 40 mpg roof mounted thule xtender 739 ski carrier with skis.

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. A roof box has in impact on both. Couldnt fit into any car parks with a height restriction or multi stories.