Just mounted a custom rack to my stock rails and my MPG dropped from 18.5 to 15.7 with the rack empty. It doesnt have a deflector yet.
Is everyone else seeing similiar drops? Seems a bit high to me.
Should add that i did the ISR mod as well but had the deckplate pre drop.
Perhaps im just laying into the throttle a bit more now.

 

Sounds about right. I used to have Yakima bars on my '95 4Runner. I would get 19-20 mpg on the hwy with it on. Off, on the same road, doing the same speeds, I would get 22-24mpg.

 

I have Thule bars on the cab of my '84, and I can't say I notice any change whether the bars are on or off.

 

A roof rack like that adds a lot of drag. Easily could see a drop like that on the highway. Even with a deflector you will see a significant drop.
I got a healthy gain in gas mileage adding my camper to my 81.

 

I've been thinking about one of those cargo basket style racks, but now I may just make do with the stock rack, and one of those plastic cargo pods I've got in the shed.

Looks good, but I can't see wasting fuel for something I won't use that often. Thanks for posting.

 

I attached it with hose clamps(ugly) but I can drop it in about 60 seconds if need be.
I'm planning to wire it with forward and rear lighting with a disconnect so I can take it off
for my DD but strap it up when heading out. I've run a few tanks now and I'm holding at
15.5 mpg, I don't see getting it much more out of it. I'm still happy with it, it can hold just shy of 2 cubic yards but I'm definitely not running it all the time. ill have to keep hunting the internets for an adaptable solution. Thanks everyone.