Roof rack design vs MPG

[Stick Figure]

While I still have a stock rack and don't plan on upgrading anytime soon, I am thinking about a modification.

In the past I have added adapters for jack and shovel mounts off the sides of the rack (<a href="http://www.mostdesigns.com/zgallery/Personal%20Vehicles/4Runner/Roof%20Rack%20Brackets">pics)</a>, and am planning on using the center for some added storage on an upcoming trip. Minimum will be fuel storage, with the possibility of a couple of larger Pelican cases as suitcases and who knows from there.

So the question is would it be worth the MPG gain to add a diffuser/spoiler to the front? Keep in mind total trip mileage will be 3000-4000 miles so even a 0.5MPG gain would be huge.

 

[e-caban]

Id say so, at least it wouldn't hurt.

 

[Stick Figure]

Id say so, at least it wouldn't hurt.

Well that was where I started to question the idea, would it actually hurt mileage more having it or not having it and the air just hit the surface of a couple of smaller squares like the gas can.

 

[e-caban]

I think if you're going to make one, make sure you have it at the right angle so the air is directed up over the cans, so you're not making an air wall having it too upright and not being useless making it too low. I would suggest plexiglass as a material as it wont deteriorate so much in the rain.

 

[drabbits]

+2 on making it the right angle, I guess thats common sense. here's a link to the fairing I used on my roof rack.
Low Profile Roof Cargo Rack - The Stingray
I actually turned the brand name in.
reduces drag, better mpg