Product Reviews

K&N Air Filter for B6/B7 Audi S4


After doing a lot of reading, I learned that most cold air intakes are not recommended for the B6/B7 Audi S4 as they tend to just suck in more hot air than anything else, so I opted for a simple K&N air filter to replace the OEM as my air intake upgrade of choice. In all likelihood, the car still had its OEM air filter from 2006 in it (despite the car being old, it only had 24k miles when I bought it so it was unlikely the previous owner replaced the air filter), so a replacement filter was more than a good idea by now. Likewise, K&N gets very good reviews by enthusiasts, and even my Audi mechanic/master tech recommends & uses them.

Installation was very simple. I followed this guide on EuroAddiction and it took about 15 minutes, using only a phillips and a flat head screwdriver. The only thing I did differently was that I took the K&N filter out of the packaging the night before to let it air out some prior to installing. A few K&N users have reported that their filter was over-oiled and literally dripping wet with oil, which could be a bad idea to install as too much oil could potentially harm the MAF (mass airflow sensor). Once the filter has sat out overnight and any excess oil has been removed or evaporated, you can pretty much pop it right in. Be careful moving the hoses out of the way, as they can be brittle – the upper radiator hose is especially fragile, so be delicate there. Once the filter is in, put everything back the way you found it and you’re all set!

K&N Filter Audi S4

So far, the K&N seems to be doing a good job. I haven’t noticed any dramatic difference (nor should I from a simple air filter), but it’s always good to replace your air filter from time to time to ensure proper airflow to the engine. An old or damaged air filter can rob the engine of horsepower and hurt fuel economy, so grab one of these for a simple, cheap & effective mod for your 2003-2008 B6/B7 Audi S4 with the 4.2 liter V8!

B7 Audi S4

Nick Roshon

Nick has been an Audi owner and fanatic for the last 10 years, and started Nick's Car Blog in 2009 to share DIYs and pictures of his A4. Currently he drives a 2012 Audi TT-RS, and has previously owned a B7 S4, B7 A4, and an 82 Audi Coupe (GT) LeMons race car. In his day job, Nick is a digital marketer and lives in San Diego, CA, USA.


  1. Hi, great blog for checking out s4 mods !
    Did the k&n filter make a better intake noise over stock? Im looking for that..

  2. Hi, Nick love the car blogs and diy I was just noticing how clean your engine bay is… WOW super clean. I was wondering if you had any tips..

  3. Haha, I think I had the engine bay steam cleaned around this time, so probably nothing I can take credit for. I do try to wipe it down in there from time to time but sadly it’s not nearly as clean right now…

  4. What grill did you buy for your B7 S4? Everyone I read on ebay says an A4 grill will not fit the S4. Thanks.

  5. Has anyone else run into the problem of the K&N 33-2209 air filter not fitting the air box? 2005 B6 S4, and if so what did you do or use instead ? Thx

  6. Hey Tom, I recently installed the K&N myself, and I too, at first, thought it didn’t fit. For whatever reason, the difference is made in how you insert the filter into the OEM box. When I put the top side in the box first, I was unable to wrangle it into place. When I inserted the bottom side first, it popped right in. Just like when you call tech support and your computer’s like, nope, nothing to see here, everything’s fine. Probably by now you’ve figured it out, bust just in case….

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