K&N Cone Air Filter.

[bajacalal]

if oiled PROPERLY... they will filter out 99.9% of all dust.. if your engine had dust in the intercooler and charge piping, then its because the PO didnt know how to properly clean and oil the filter..

he either used compressed air (and blew the gauze apart) on the filter, or didnt use sufficient oil...

The oil eventually migrates out of the filter and then it lets the dust through. I bought the truck from a cement contractor and it had like a mix of concrete dust and desert dust on everything (including the intake).

You can keep re-oiling it, but then you're oiling your air filter every other weekend and that's just silly. That's basically an oil bath filter and there's a reason they haven't used those things in 50 years... they let dust through and you have to oil it every weekend! It's not just that I think they're ineffective, but also inconvenient. When I had one, it always seemed to take forever to dry. I'll take the convenience of the paper filter which is highly effective as well.

745 has the right idea, as far as the kind of conditions I'm concerned about. Around here TONS of people have trucks they use to go out to the desert with to camp and ride dirtbikes and it's really dusty (which is NOT the same as mud, I hate mud) and they use K&N filters because "it makes it go faster" and I'm always saying "NO!!! You're killing your engine."

I will say that the brand of air filter you use does have an effect though. I wound up with a couple of cheapie air filters that fit the VW and they did not work very well, there was a noticeable decrease in power and a noticeable increase in smoking compared to the German ones I usually use on these.

[745 turbogreasel]

The oil eventually migrates out of the filter and then it lets the dust through.

Everything I know about filters says oily dust in the filter will be tacky, and stick more particles more effectively, but at some cost to flow.
I sometimes re oil mine once between cleanings.

[homerj1]

So the bottom line is? 

[8v-of-fury]

What are your power goals? Because I am pretty sure I have seen people make 200whp on these engines with the stock air box and stock Mann air filter..

Final verdict for any 1.6 or 1.9 VW diesel?? Waste of time and money.

[745 turbogreasel]

How does it cost more if it will outlast the car?
Mine lists at $25, which adds up to a $46 K&N real fast.

[8v-of-fury]

Time is money, do you not value your time? Do you have all the time in the world to be cleaning your air filter every weekend?

With all that time lost, it adds up. Assuming 200,000 is the life of the car.. you could replace the stock filter every third oil change (15k) and be at the same basic price.

13.3 changes, at $5 a pop. $67. Much less PITA, no oiling, no wasted time for no gains on one of these engines.

EDIT: $25?? You're being bent over. 

[745 turbogreasel]

No I'm not, I don't buy them.  That just dealer list price.
I clean my filters maybe twice a year, and for one of the cars I have an extra, so down time is 0.
It's a 10 or 15 minute activity while sitting in the sun having a beer.  Doesn't feel wasted at all.  Especially if you do it while waiting for oil or coolant to drain, glue to dry, or whatever.
I cheated on the price of my K&N, they were $3ea. at pick N Pull, just like any other air filter element.
For $45 delivered, I would not have got the spare.

$5? lowest I see for you is

$5.12
$12.26 with est. tax & shipping
RockAuto.com

[theman53]

I actually own several K&N. It is a money saver in the long run. You do not have to clean them every weekend. I cleaned my diesel air filter whenever I started seeing black smoke more than normal. It is easy and until you have one you will not understand. If you have a really dusty area or track they make a thing called a pre filter that helps with loose dust from clogging the main filter. I have only ran one and liked it for what I needed. The prefilter is un oiled and cleans by shaking it off.

[R.O.R-2.0]

How does it cost more if it will outlast the car?
Mine lists at $25, which adds up to a $46 K&N real fast.

you HAVE TO replace the paper filter..

TD air filters are NOT cheap around here, unless you want some cheap no-name, white box vato-zone, or O'reilly garbage..

my K&N filters cost $5 at u-pluck-it.. thats LESS than a brand new cheap paper filter..

my intake tract is ALWAYS spotless..

IDK dude.. they run K&N filters on rigs that run the Dakar rally, the Baja 500 and 1000, as well as plenty of other dusty races..

im gonna stand by what i said, if they are cleaned and oiled properly, they will filter almost as much dust out of the air as a paper filter, but with ALOT more flow..

im gonna say that the guy you got your truck from, was an idiot, and probably used compressed air to blow the junk out of his K&N filter, and blew the gauze apart, leaving big holes in the filter media, just letting dust RIGHT THRU..

ive run K&N filters on ALL of my ATVs and motorcycles.. they are often times ridden in VERY dusty conditions.. and ive never had a dirty intake duct, or dirty carb throat either..

(plus, another reason to run a K&N filter, is when you CANT or dont want to run an air box.. ALL of my charge/intake piping is on the same side, so i have NO ROOM to run a stock air box on my car.. i would have to re-locate too much stuff to make the TD air box work, but a K&N pod fits nicely)

[RabbitJockey]

I would like to see a scientific comparison of k&n vs a good paper filter mostly a Mann because they are thick as hell, or even a wix filter.  I don't think they're trash or anything I'm just curious how much better they are. Anything is better than fram

[theman53]

I would be willing to concede that a paper filter lets less dirt through than a K&N. At the same time it lets a ton less air through as well. Neither are 100% so to me it becomes what is an acceptable level. I like the K&N, so I run them. I don't think anyone would say that the engine will blow up if you run it for 15,000 miles, so I say try for yourself and if you don't like it someone like me would buy it off you. I had put lots of money into my 1.6 build and it never had a paper filter on it. After 40,000 miles the rings and bores looked as good as new...except #3 which had holes in it from the precup, but the cross hatch that was there looked awesome. I drive 50% dirt roads 50% paved in some form. I can only say how it works for me and I have no problems with them

[ORCoaster]

Just to satisfy the curious.  TrevOrbr you asked:   I would like to see a scientific comparison of K&N versus a good paper filter.  Is this science or fantasy?  

http://www.nicoclub.com/archives/kn-vs-oem-filter.html

Or this one,   

http://www.bobistheoilguy.com/airfilter/airtest1.htm

[tyb525]

Paper filters out smaller particles and flow less air, are cheaper, and aren't reusuable.

K&N filters slightly worse than paper, flow more air, are reusable, and are more expensive initially.

Pick your poison, I don't think it as big of an argument as people on the internetz make it out to be. Kind of like the argument whether amsoil is actually good or not. I really don't care either way on the matter, I would run either filter and I have run both kinds on various vehicles and haven't had problems with either.

Anyone else notice that first link seems to be biased towards ac delco? their products have always been viewed as pure crap by every mechanic I've known.

[RabbitJockey]

itd be interesting to use one of those obd2 plug in programs that lets u monitor lbs/min of air flow and change filters and see if there is any difference too.  the one site seems to show only small gains but he is only showing one flow rate,

[745 turbogreasel]

the second test is a bit flawed, he's sucking all the air through a 3" square of filter not even pleated. This has to yield a much higher velocity and pressure than you cold ever hope to achieve with a full size filter. 
Also where one filter has 7 pleats, and another has 15, it won't show a difference despite one having 2x the area.