[Christ]

I use a round cone type filter, but it's a stainless steel mesh, like 4 layers thick. I haven't really tested it for airflow or anything, but it sits in the same location as the stock filter did on my Civic, and with the 3" mandrel bent "cold air intake" (eBay special) it seems to be working fine. Oil changes haven't shown any evidence of crap in the engine, and I drive on farm roads with it alot.

The car is sold, but I'm keeping the filter, I'll probably put it on my wife's Grand Prix for now. It's a serviceable filter, that apparently will last "nearly forever". You clean it with warm soapy water, just like your dishes, and there is no oiling necessary. APC makes it. (I know, I know... )

I've personally never seen a gain from K&N filters, and don't plan to speculate on why or why not. I don't care to pay the kind of money that they cost, and then maintaining the filter beyond that, and the vehicle maintenance issues that they're apparently known to cause. I'd rather use a "normal" serviceable filter, like the stainless mesh I have now. IF I ever feel that it's not performing on a particulate filtering level, I'll just add a washable pre-filter to it. (ShopVac FTW!)

To hush the speculative claims that increased airflow through the filter causes better fuel mileage in typical scenarios:

This one is simple, and I can't believe that no one has thought to do it.

If you think your OEM filter is restrictive in normal situations, I want you to set your engine at a specific RPM with the throttle, and have someone watch the tach, or hook up an external tach that you can watch.

Loosen the clamp that holds the air pipe to the filter box, and remove the air pipe from the filter box so that the engine is now "breathing freely". If you notice a change in engine RPM at this point, your OEM filter is creating restriction in your normal driving situations. If no discernible changes are noted in RPM, your air filter is NOT creating restriction in your intake tract.

Another way to test this is to go buy a K&N intake "drop-in" filter. Measure the vacuum at the pre-filter opening in the intake tract, both at idle and at 20% throttle with 0 load using your OEM filter. Use the same procedure to test vacuum at the pre-filter intake opening with the K&N filter installed. The figures at both idle and 20/0 should be either exactly or nearly exactly the same (no more than .5 inHg variance) for both tests.

If they're not, the OEM filter is restrictive during normal driving situations, and the K&N filter may provide some flow benefit for you.