Ever wonder why they sell a lot of fender liners on ebay?

 

These are cheaper version of a ground effort kit. At freeway cruising speed, most of resistance to prevent a tire moving comes from air drag. See tirerack's technical paper.
http://www.tirerack.com/tires/tirete....jsp?techid=29
The mudflaps come after tires and are detrimental to aerodynamics, one can remove them for less noise, a little more power and better mpg.

 

Now, you are making me think about the mudguards I put in!!! No, I am keeping them.

 

So, if these two 2x2" flaps make such a difference, how come nobody is out there installing a full front air dam to reduce under the body air resistance. I brought this up a few months ago and the consensus seemed to be that it would not increase fuel economy much. Now I am beginning to wonder!

 

Because no one will pay for it except performance oriented drivers. Full body kit also lowers the ground clearance, if the car is lowered, you will have problem clearing some curbs.

 

I saw these flaps on the Sienna (the 3.5 L model and I will be getting back to you later on what I think about engine mods on this engine).

 

I agree, you need the ground clearance, but ONLY when you are going off road or in a big snowstorm.

I was thinking of adding an air dam that was easily removable. Something held on by 6 wing nuts, or something like that.

 

Work on it....looks like a good DIY project that could assist in performance.