Will a rack affect the gas mileage of the vehicle?
The simple answer is yes, by adding a rack you are increasing the drag and weight of the vehicle and this will certainly change the gas mileage vs not having the rack.
How much will it affect it?
That question is much more difficult to answer. There too many variables for us to provide a specific number and it is not something that we test for.
There are a number of articles on the internet and the percentages range from 10 to 50%.
Can I do anything to improve my mileage while the rack is on the car?
Yes, it is the same things you can do to improve your mileage without a rack.
- Avoid hard accelerations
- Maintain a constant speed
- Slow down in heavy winds