Tundra roof rack on cap, cargo box, mpg q's

[nctacoma]

Trying to weigh out the fuel mileage loss I will suffer if I put a roof rack on my pickup shell on a 2008 tundra 5.7l. We are about to embark on a multi-month road trip and are weighing the benefits of being able to bring surfboards and a Yakima cargo box for extra storage.
I know how much of a difference it makes with cars, but what about on a truck that already gets poor gas mileage. Will I go from 16 to 15 or 16 to 13?

Any thoughts?

 

[OTR]

It depends on what speed you are driving at down the highway. When I had my RTT on top of my cap I believe I avg around 14/15 mpg around 70 mph if my memory serves me correctly. Once I get above 70 it starts dropping fast in my truck.

I would take everything I needed and just do the trip. I figure what a few extra bucks for the convenience of having everything I want or want to do. I get really bummed if I say "I wish I would of brought ... or did....." while on the trip.

Other options??
-If you have 2 people going on the trip and have a double cab or a crewmax, you could take out your rear seat and get a few rubbermaid containers stacked up in the back for increased storage.

-I use rubbermaid containers in the shell to organize most efficiently.

-Could you rent some surf boards once your at you location????