Rep Power: 190

I haven't put a lip kit on yet (it's like 15 degrees outside) but I was wondering if a front lip would affect mpg at all? I've googled it and searched but there is very little on the subject. On one hand I think it would decrease mpg b/c the car has a little more surface area but on the other hand if you look at the way lips are shaped, it looks like they are curved to put more airflow around the car or over it rather than under it. Since the bottom of the car is a wind trap, this might counteract the increased surface area. Opinions?

 
Rep Power: 235

To get a noticeable increase you would have to have the lip riding right on the road surface. With our cars the increase/decrease will be so insignificant you probably won't be able to tell a difference.

 
Rep Power: 518

I had a customer tell me that he found a consistent 1.5 MPG drop on the highway when his car was wearing a bra with 2 little deflectors that stood up on top of the hood. It was an older Mazda 626 turbo.

My dad claimed a consistent 1-2 MPG gain after switching Moms old 86 Accord from 10w30 to 5w30.

If you have been religious about calculating your mileage up to this point in time, you may notice a small change after adding the lip.
Frontal area increase may or may not be offset by any aerodynamic gain under the car. ( cd )
Your mileage may vary.

 
Rep Power: 190

Well I guess I'll have to find sometime this summer then. I plan to lower it and add a lip so lowering it should give it a minor mpg bump and IF the lip decreases mpg then it should come out to about equal.