Alright I know its been said but how much dose a roof rack really kill your mpg. I've be thinking about getting one to free up some space in the back plus I already have a lot of weight back there but wanted to maybe mount the spare. Also would be nice for throwing some vacation gear. Spare wont always be there. I don't have a lift 235/75 15 tires might have a 3 inch lift by the End of the year as of now I get 19 high way 2000 cherokee auto Chrysler gear

 

I have a roof rack . . i cant say how many mpgs you will lose, but i will say its a jeep and they get horrible gas millage as is . . be it that you have no lift and small tires it wont make a huge difference . .

 

Empty you'd probably see ~2mpg loss. Up to 5 or 6 with gear.. Depends on design, if it's got a deflector, gear, outside windspeed..

 

I also lose 2-3 mpgs when I have mine on, which is why I pull it off when I don't need it.

 

Idk about 5 or 6 unless you have a fridge strapped up there . . i have a full size spare a hilift a shovel and some lights and its a surco so its flat and ive lost probably 2 at most but thats with a lift and 33s as well and a misfire

 

I had a large Thule combi box on my roof for 2 tanks worth of mixed driving (more city than highway) and got about 18.9 to 19.3 over the course of tanks. I took the box off and have run many tanks of fuel through the same type of driving. Without it I cracked 20 mpg on 1 tank (barely, it was like 20.019) and typically am in the mid 19 mpg range.

Based on my results it's probably going back on again because quite frankly I like the way it looks an the loss of mpg is barely noticeable. I was hoping for a solid 2 mpg gain without it but saw nothing like that in real world results.

 

I'm thinking about making an emt one but not have anything on it just for looks behind my light bar. I doubt that'll effect mileage, it mostly depends on the weight that's going up on there