I've had a bike rack for years, but never really bothered to calculate the hit on MPG. About a month ago, I was really curious how much MPG was affected by my bike rack up top.

My set up: It is a Yakima system. Q-towers, 48" round bars and a Copperhead (?) bike mount (has a fork mount and strap for rear wheel). Also a wind fairing. All set up exactly according to M-measurements on the Yakima site.

Fit: 2007 Fit Sport 5-sp manual. 62k miles. 195/55/15 A/S tires. All stock.

Driving conditions: 90% highway commuting to work. Terrain is semi-hilly, but not much elevation change. I usually go 72-75MPH. Usually zero traffic, so no stop-n-go.

First, I had the roof rack off to get a baseline. I tracked it for about a month period (in June). I didn't include months prior, as some gas stations were still using ethanol and temps were way below what they are now. I wanted the least amount of variance in driving conditions as possible.

Without roof rack:

Miles: 2,027
Gallons consumed: 51.057
Average MPG: 39.63

With roof rack:

Miles: 555.7
Gallons consumed: 14.519
Average MPG: 38.36

I was somewhat surprised that there was only 3.2% change. I was expecting something like 10%. This minimal hit means that I don't feel bad just leaving the bike rack on the car.

I am going to continue to monitor the MPG with the rack on for another 1,500 miles and compare again. I will also conduct tests without the fairing to see if that makes any difference.

Just thought somebody might be interested in these findings.

 

That's very interesting. I would have thought it would have been a lot closer to 5 - 10% as well.

-Dustin

 

Thanks for posting this. Very interesting.
My only issue is when I have the rook rack system installed that usually means we are traveling for lacrosse which means the car has AC On, 3 people, plus gear, plus a loaded skybox... Its way more than 1mpg deviation.