Impirical data on fuel economy - after market bumpers?

Watching how water sits on the hood of my 3rg gen at freeway speeds, I'm guessing aerodynamics weren't a priority for Toyota. How much worse could it get?

Does anyone have any imperial data of fuel economy with different front bumpers? I'm expecting the worst to be the tube style with larger cutouts in front of the tires.

 

I'm guessing you'll have to go a few places to the right of the decimal point to see any difference.

 

Weight would play a larger factor than aerodynamics but it would be rare to find real numbers of the difference with no other changes. Both my trucks have aluminum bumpers and I track every fuel up on Fuely so mileage is tracked for 10s of thousand of miles and there doesn't seem to be an appreciable difference between average fuel mileage for me.