I was thinking about using a K&N air filter. I heard it improves performance and gas mileage.

Does anyone have any experience with these air filters? Please share..... 

Does the product advertise performance improvement? What specifically does it say? 

I put Kn filter on my truck havn't notice any change. If you keep your foot off the pedal the filter my help. I also put nitrogen in my tirestruck rides nice and handles better.
but for milege i think i lost milege. gassaroo est my miledeg at 13.4 

I went ahead and took the plunge and installed a K&N drop-in air filter today.

I'll continue to track my mileage and update, what, if any, mileage improvements I notice. 

Ipreviously had a K&N filter on my previous truck, didn't notice a difference.
If you look at the structure of the fibers, the Amsoil filter should filter better, last longer, and still have excellent air flow, but I don't think I noticed any MPG improvements either. 

As stated earlier, I have justed installed a new K&N Air Filter in my 05, PT Cruiser.

I do not have any gas mileage numbers yet, but both me and my wife have noticed a pronounced increase in performance!

It seems like a totally different car. I should have my first tank of gas used in about 1 week. At that time, I'll post the mpg on that first tank, and the difference, (if any) from what I have been traking over the last seven months. 

First full tank with the K&N Air Filter - 22.7 mpg, with is 0.2 more than the previous tank, but consistent with my previous fill ups.

I have read that it take about 200 miles of driving before the cars computer notices the different air mixture in the gas, and adjusts accordingly.

So, with over 200 miles driven now, my next tank should be an indicator of what is to come, as long as my driving patterns do not change.

Stay tuned..... 

Ok, the second tank is in the books now. That tank was 23 mpg. Good, but I was seeing this before K&N, but at least we are trending upward.

I have to keep in mind that about 90 miles of that tank was used on a trip that I do not normally take, a trip that has historically increase my gas mileage.

Will K&N continue to trend my gas mileage up, or will the next tank trend back down.....

We'll see.... 

Ok, latest gas mileage update: I got 24.6 mpg on my last tank. That is about a 1.5 mpg increase in what I was getting before using a K&N air filter. That is great, but it is only one tank at that level.

Lets wait and see if this continues.

Also, since I have been tracking this, my driving route to work has changed for the better. Far fewer traffic lights. So, at this point, we are now working with two variables, so it may be impossible to get definative proof if any mpg increases come from the air filter.

More to come..... 

OK, it is time for me to close my findings.

FACT: The K&N Air Filter has improved the overall performance of my PT Cruiser. There is a noticable improvement in the cars' get up and go!

Now, about the improved gas mileage: Since I changed employment during this experiment, and my drive to work changed, I can neither confirm, nor deny any gas mileage improvement.

Therefore, I cannot justify the cost of the K&N air filter on any gas mileage improvement claims.

That being said, I do enjoy the performance improvement, and also factoring that I will not have to replace the K&N Air Filter, I do recommend its purchase to anyone looking at this post.