Roof Racks and Fuel Economy

[JT646]

Detailed writeup from Autoblog site. 


http://www.autoblog.com/2016/04/28/roof-racks-fuel-efficiency-study/

The short version: Up to 25% fuel consumption penalty.   Some of us don't have a choice  but travelers that put on a lot of mileage might want to modify what they put on the roof...and possibly save a few $$$.

 

[steamjam1]

Hmmm.. I have an off road roof rack on my 4x4 van now, and it useto have a thule cargo box to go with it. I didn't notice any penalty in gas mileage even when loaded down. Then again it prolly doesn't matter on Dodge vans because they don't exactly "slip through the wind like a knife" More like "brutally ramming through the air with a cinder block."

 

[JT646]

Then again it prolly doesn't matter on Dodge vans because they don't exactly "slip through the wind like a knife" More like "brutally ramming through the air with a cinder block."

Good point.....probably much more noticeable in a smaller vehicle, but I would expect the % losses to be about the same.  Example: A 10% loss in a 40 mpg car is 4 mpg vs 1.2 mpg in a 12 mpg camper van.

 

[GotSmart]

The numbers do not add up.  

My mileage dropped 1/2 mpg (.5) out of 15 highway.  or just about 3.5%

This is in my flying brick with solar panels attached. 

Now if I had a bicycle strapped on it, that would really catch the wind and cause a much greater decrease in mileage.

 

[steamjam1]

The numbers do not add up.  

My mileage dropped 1/2 mpg (.5) out of 15 highway.  or just about 3.5%

This is in my flying brick with solar panels attached. 

Now if I had a bicycle strapped on it, that would really catch the wind and cause a much greater decrease in mileage.

I got the same when my van was still a 2wd. 15mpg. When I added the roof racks and the such. No noticeable change to mpg. As a 4x4, it now gets 13mpg. I should remove the rack and see if it makes any difference. Or add a fairing to the front of the rack and see what happens. (likely nothing)

 

[Every Road Leads Home]

I did a test on my old 03 Chevy Express years ago. Did about 2500 miles with roof racks and a ladder and with no roof racks/no ladder and only ended up being less than one mpg difference. Seeing as how I didn't drive the same speeds/same routes/same weather etc for each of the 2500 mile tests, I don't know if the roof racks caused the loss in mileage or just the different driving conditions. Never really noticed much difference hauling heavy loads either. I think the smaller vehicles/smaller engines suffer more when hauling weight, roof racks, etc.

 

[masterplumber]

On my Ram 2500 I took my ladders off the rack, but kept the rack. I noticed about 1/2 mpg difference. I doubt I would see another 1/2 if I removed the rack as it doesn't catch nearly as much air as the ladders did.

 

[highdesertranger]

those  that remember my truck from RTR should remember I have a monster roof rack.  for those that were not there here it is.



does  it effect my MPG?  probably.  do I care?  not much.  I need to carry gear,  so I just use it.  after all my truck is like driving a barn down the road as far as aerodynamics.  so in review, either you want(need) a rack or you don't.  highdesertranger

 

[Gary68]

in one of bob's video there is a guy i believe in a prius that reported dramatic lose with a canoe on top,a rack by itself wont make much difference but a rack with bikes and an ice chest or two will
just get up to highway speed and stick your hand out the window now times that by four and thats about the drag of your side view mirrors,your engine has to make up for that costing mpg