I just got a new K&N Cai for the hemi. I know it is garuenteed to put out more hp (about 10). Does it help gass mileage at all?

 

No, not really no.

 

does it decrease?

 

Yeah, cuz you will have it wide open to hear the moan

 

thats true but ive heard its easy to get a 1-2 mpg gain.

 

You are going to get either more MPG or more HP. When taking advantage of the extra HP you aren't going to be getting good mileage, or when taking advantage of the fuel economy you won't notice anymore HP.

 

Both HP and gas mileage are gonna be hard to notice. But they are both gonna be there

 

IMO the real advantage of a CAI is it really helps other mods. It won't give much of a HP gain (that 10 claimed turns out to be 3 or 4 RWHP) nor any noticeable MPG gains. When used in conjunction with some other mods such as cat back, headers or even a tuner, the combined gain can be much greater than the sum of the components individually.

 

unless the louder noise makes you unconsciously slow down
there will be no MPG gain from a CAI

this is the 'flip side' of the experience many of us have had
where you are driving a very quiet vehicle
look down at the speedo
and find you are traveling 15 to 20 MPH faster than you thought

but if you are willing to tolerate a loud vehicle
go for a loud exhaust that has lower backpressure too