Effect of cartop carrier on mileage?

[Bobbie Mayer]

I have a Thule box I used on my old Forester. I believe I was getting slightly better gas mileage with that while towing than I am now without it on. Does this make sense? Is it acting like a wind deflector? The trailer is taller than the Subaru so it kind of makes sense, but I just wondered what everyone else thinks.

[Carol H]

Bobbie I have used a Thule low profile box on my Outback in the winter and all I can say for sure is that it doesnt negatively impact my mileage - but I haven't tried it towing so cant say for sure but based on design of it I would not think it would.

Looking at the front profile of your trailer it may well be helping out and acting as a bit of a wind deflector.

[Mike Magee]

A kayak on my car reduces my fuel economy, towing or not. Never used a Thule box, though.

[kirkman]

I bet it does!

[Thomas G.]

Everyone knows that a Thule box creates a forward thrust that negates the added frontal area.