Did a quick forum search and couldn't find anything, so sorry if this has been brought up before.

A friend told me that the rear wind deflector on my 4 runner kills my fuel mileage. Is this true?

Thanks.

 

? Well I've never heard that before. I think the purpose of that spoiler is to keep dirt off of the rear window.

 

Yup, it's there to keep dirt from sticking to the rear window and helps keep the airflow up to expel the exhaust gases further from the truck.

As with anything you put on your 4Runner, adding surface area to the exterior is going to increase drag. But does it really harm your MPG that much? Probably not. I got my MPG average up a whopping .3 MPG by taking off the roof rack, but I took it off as a personal preference, not in hopes of gaining MPG.