Guess the mileage drop on this Prius C with loaded roof rack
 

So my neighbor has this Prius C, and gave me permission to post to EM.
Year round, she drives with an empty roof rack, and sees " about 42 MPG "
( This is just the uprights and two crosspieces, and not the setup you see here. )
I asked her to glance at the F.E. the next time she drove.
Trip was " around 65 mph on mostly highway. "

The couple normally drive a Subaru suv / station wagon type vehicle, and her boyfriend says he only sees around a 4mpg drop with this same setup on that vehicle.

This is their " Battle Prius " as they call it.

So what do you all think ?

Could be lie-O-meter mileage, my golf reports 50, the gas pump says 43. I thought a 10% minimum reduction, but I don't know what the reported should be.

I got about a 20% range loss putting a 52 inch light bar on my leaf. Good thing I went with the magnetic mount.

I'll let you guys know the answer next week.

My 98 Suzuki Esteem got around 40. Put an Xmas tree on the roof and go on the interstate? 20 mpg. I voted 31 mpg here.

35 MPG was the result.

I win!