I'm wondering if there have been any definitive studies on the efficiency and/or performance gains from replacing an OEM air filter with a washable, "higher flow" model from someone like K&N.  Or does anyone just have an experience they care to share?

"Higher flow" might mean more dirt getting into the engine.  You might want to read the following comparison between different air filters:

http://duramax-diesel.com/spicer/index.htm

I've got a K&N in my '00 Subaru Outback. I don't think it offers any power advantage but they are considered safe IF you maintain them. I wash and replenish it at regular intervals and the cost of doing so is so low that over time it will save me some money. I've had mine in the car for about 10 years and it's still going strong.

Don't waste your time or $$$ these things are nothing but hype and offer NO advantage. They claim higher airflow......BS. What on earth do you need that for on a stock vehicle anyway? They claim cost savings in fuel.......again BS if they did result in more airflow than more fuel would be admitted. They claim cost saving over paper..again BS think about how many GOOD normal filters you could buy over the life of your car changing at 15 to 30k miles (normal intervals) you could buy. They are good at ONE thing...........increasing the flow of $$$$ out of your wallet for buying them and the possible harm to your engine from excess dirt.

They aren't that expensive. I like things that get reused, like K&N filters. They're one less thing to stick in the landfill.

Thanks to you all for your posts.  I appreciate it.

They aren't that expensive. I like things that get reused, like K&N filters. They're one less thing to stick in the landfill.

I'd be worried more about K&N filters allowing more dirt to get into the engine than the stock (AC Delco in the case of the GM truck in the web page linked above) filters.

Also, for some cars, the oil that comes off of those filters is sometimes blamed for failures of mass airflow sensors and the like.

Not that product success has anything to do with anything...but K&N makes a reputable product. Risk? I'm sure there are other ways to clean the air going into a car but I think the K&N filters out all the dangerous particles. I'll post up in another 100k miles to tell you if it ruined my engine. ;-)

I use the paper type and routinely get 2-300K miles out of my vehicles before I  get rid of them. Just how much better can a K&N filter be?

I like the idea of reusable products. Less waste.

It'll just get your engine there faster imo

good one :-)

Gently blow the paper filter out with compressed air or use your shop vac to clean it. Then when you do throw it out, use a utility knife to separate the plastic and paper and put them both in the recycle bin.

Reuse and recycle...

Got to love recycling. Still... even recycling brings added waste. You have to transport materials to a recycling center, and it take labor and energy to sort and process recycled materials. The benefits are limited, compared with reuse at the consumer level.

I don't want to sound overly enthusiastic about what a K&N filter can or can't do for the OPer but thought I'd balance the otherwise negative comments with my own positive experience.

I'll tell you a while ago when I was looking for another vehicle I actually passed on one that I REALLY liked but the guy had been using a K&N. I just didn't want to inherit the issues I knew would come ...........fouled sensors, excess dirt, etc.

Somehow, I doubt the amount of paper and whatever other material contained in five to fifteen paper air filters over the life of a car of a decade or few is significant compared to the amount of paper discarded or recycled by a typical person or household in the US during the same decade or few.

Especially if you use any disposable paper products to clean the dirty oil off of an oiled air filter (and whatever else the oil gets on) before re-oiling it.  Also, if the additional dirt let through causes the engine to require additional repairs, or the oil gets on sensors that need replacement, that will likely have a much greater economic and environmental impact than the paper air filters.

...I knew would come...

You're laying it on a little thick!

Nope I am not. I really did and I told the seller same too. I knew the issues that could come up (especialy on GM vehicles) because of how sensitive their MAF sensors are. Just did not want the possible headaches