K and N Air Filter Review: Save $1100 On Gas!

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We’ve spent a lot of time reviewing cold air intakes here on TundraHeadquarters.com, and for good reason. Cold air intakes offer increased performance, improved gas mileage, go-fast looks, and a great sound. These kits work because they increase air flow into the engine while also making an effort to ensure the intake air is as cool as possible. Unfortunately, while they do work, cold air intake kits cost $300-$400.

K and N air filter saves gas.

For years, K&N has been offering a less expensive alternative to cold air intake kits, specifically, a high-performance air filter. K&N says that their high-flow air filters significantly increase air flow and therefore offer many of the same benefits as more expensive full-fledged intake kits. We decided to check that claim, and here’s what we came up with:

1. Performance. While there was no significant gain in measured horsepower (all our test runs were within normal hp variance), there was a noticeable improvement in throttle response and engine performance at cold start.

2. Fuel Economy. Get your wallet ready – if you don’t already have a K&N air filter (or an air intake kit), buy one now. We noticed more than a 0.50 average improvement in mpg on our test vehicle over the course of 2 weeks and about 800 miles. Before we added the K&N, our test truck averaged 14.3 mpg. After the filter was added, the test vehicle averaged 14.9 mpg. That means that over the course of our test we saved 2.3 gallons of gas. Put another way – spending $50 on a K&N air filter that improves your mpg 0.60 will pay for itself in about 5,000 miles – if not sooner. If you extrapolate out to 100k miles, our test results show that the K&N performance air filter will save you about 280 gallons of gas. That’s about $1,100 in gas savings!

3. K&N Million Mile Warranty. If the gas mileage improvement isn’t enough incentive for you to buy a K&N air filter, here’s another. K&N’s performance air filter comes with a 1,000,000 mile warranty. As long as you clean it (every 25k-50k miles), it will last forever. The factory air filter (made from paper that is more restrictive than the cotton gauze K&N design) should be replaced every 15k-30k miles, at a cost of $20 per filter. The cleaning process does require you to buy a $20 re-charger kit, but even if you pay $60 for the K&N filter and $20 for the cleaning kit, you still break even after replacing four factory air filters (which can take 60k-120k miles, depending on how dirty your filter gets). Not to mention the gas savings…

K&N air filter installed.

We installed the K&N performance air filter in a 2007 Toyota Tundra double cab with the 5.7L V8 (above). Thanks to Larry for providing his truck and allowing us to test K&N’s air filter.

4. Factory Warranty Issues. There are a few rumors out their that adding a K&N air filter (or similar) to your vehicle will ruin your mass air flow (MAF) sensor. Some of these rumors are true – if you clean and then grossly over-oil your K&N air filter, the excess oil will enter your air intake and could foul your sensor. As long as you’re careful, you won’t over-oil your filter when you clean it. K&N has a decent explanation of why their air filters can’t hurt your truck, but the best explanation follows. TRD also sells a cotton-gauze performance air filter just like the K&N filter – they also offer a cleaning kit, just like K&N. Since TRD sells a nearly identical part for a new Toyota, you’ve got nothing to worry about.

5. Alternatives. There are a few companies that sell performance air filters similar to K&N – aFe, TRD, and FRAM might be the best known. Since we haven’t tested any other performance cotton-gauze air filters, we can’t say for sure that these other brands offer the same benefits. But it’s a pretty safe bet that they do. We would definitely recommend the K&N air filter over the TRD unit simply because of the cost. As for the rest, since there’s no substantial price difference, there’s no reason not to choose the K&N.

K and N air filter saves gas.

Our test of the K&N air filter showed an average 0.6 mpg improvement. Extrapolated to 100k miles of driving, that works out to about $1100 in gas savings (assuming gas costs $4 per gallon).

Bottom line: If you like fuel economy and better throttle response, buy a K&N performance air filter. They cost about $50 now, and between the million mile warranty and the gas savings (we calculated $1,100 dollars worth over the course of 100k miles), it’s a no-brainer.

Check prices on AutoAnything.com (where shipping is always free), Auto Parts Warehouse (sometimes offering a 10% discount on K&N parts), and 4 Wheel Parts. Between the three, you should be able to find the best price…just make sure to include the shipping cost into the final figure. Some online parts sellers discount the part but then add on $10-$20 in shipping and handling charges, so watch out.

Filed Under: Toyota Tundra Accessories

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  1. TXTee says:

    I opted for the entire K&N cold air intake kit for my 08 Tundra 5.7L and so far I love the more aggressive sound even though I also have dual FlowMasters. It definitely has more throttle response and fuel efficiency has somewhat increased as well. I tested it on a 2000 mile return trip from Houston to North Bay CA and no complaints or issues. There are some improvements versus stock vehicle but it’s all up to what you’re looking for long-term. I would suggest that you get better hose clamps than what K&N provides because I had a lot of trouble with the air cleaner sliding right off the throttle body. I want to be able to punch it and not worry about things falling off!

  2. Jim Mateer says:

    I have had two K&N filters foul 2 MAF sensors, straight out of the box, as oiled by the factory. The first was on a 2004 Ford F150, and the second on a 2007 Chevy Silverado. Once I figured out the problem, it was a simple matter to get some spray electrinics (contact) cleaner and hose off the MAF. I then cleared the ECU code, and all was well. It is not a big deal, and the advantages of the K&N offset the inconvienence, but it does happen.

  3. Anonymous says:

    Sorry you still have to buy oil for the filter and only 1,000,000 mile warranty not a lifetime warranty. I’ll stay with my AFE Stage II lifetime warranty and no oil to even come close in messing up the maf sensor. Not to mentiuon I got an increase of 1.5mpg.

  4. Mickey says:

    My comments above.

  5. Mickey – Good point.
    Jim – A factory-oiled K&N cotton gauze filter shouldn’t be clogging MAF sensors…yet the rumors persist. K&N sponsored an independent study that showed fairly conclusively that their filters aren’t clogging MAFs, so we stand by our assertion that this is at best a rare occurrence.

  6. john says:

    I had a K&N filter clog up my map sensor a few years ago. Maybe I oiled it to much or oiled the wrong side. Whatever happened it scared the shi?? out of me cause I thought my truck was ruined. Kept shooting carb cleaner untill I somehow managed to unclogg something. May be someting I did but I changed to paper fram filters and have stayed with them since.

  7. tmac says:

    bought the k&n cold air intake and must say im impressed the sound is awesome so much more aggressive than the stock sound of the truck (wich sounds more like a camry).
    power and throttle response is improved and i gained 1 mile per gallon, how can u complain about that…

  8. tmac says:

    actually i hafta make a correction on that i didnt buy cai my girlfriend bought it for me for xmas..
    god bless her

  9. tmac – Sounds great man – 1 mpg is awesome. That GF sounds OK too…it’s love when they buy stuff for your truck.

  10. Carl Sampson says:

    I recently bought my first Tundra (2008 4.7 DC TRD 4X4) and it needed an air cleaner change so I went with the drop-in K&N filter. Feels and sounds like it has a little more power but I haven’t had the K&N installed long enough to check gas milesage. My question is, what is that cloth-like filter that is rivited in permanently to the air box cover? It seems like it would cause airflow restriction. If a cold air kit was installed, this filter in the air box cover would not be used so what is it’s purpose? I’ve asked two different auto part stores and the service manager at our local Toyota dealer and no one knows what this filter is for? Can it be removed to increase air flow?

  11. Carl – That filter has two purposes. First, it’s meant to block any really big “junk” from getting into the paper filter. Second, it’s a noise reducer. Removing this filter is an easy way to boost your stock intake’s power, but unless you also replace the stock paper air filter with something more durable, it’s a bad idea to remove it. Does that make sense (I don’t think I explained it very well)?

  12. Carl Sampson says:

    Thanks for the quick response. The filter I’m referring to is down stream in the air flow path, meaning the intake air has already been filtered by the air filter so I don’t know what your comment of “to block any really big

  13. Carl – I thought you were referring to the filter in the bottom of the air box lid (hence the term air box cover). I haven’t noticed that filter before – perhaps it’s exclusive to the 4.7. The only functions I can possibly think of is that it either somehow protects the MAF sensor (which I sincerely doubt) or it’s designed to absorb moisture (also doubt that as well). I can’t think of any reason for it’s existence – if the air filter is doing it’s job, there’s no purpose in a second filter in the tube. I say remove it.

  14. THUNDER ROAD says:

    i got the K&N 63 Series air filter. bought two filter so one can dry. when the other one is on the truck. i got a mbrp performance exhaust both sound good together.

  15. Ralph says:


    Hey I know have a question with regards to the k & n drop in filter. I think I am going to go this route first due to cost factor. I am a little confused though by the comments of “pre-oiling” this filter before inserting it. I thought K&N’s performance air-filter (part no.33-2387) came ready to install. Is it ready to install or is there any prep work required?

  16. Jason says:

    Ralph – It’s pre-oiled at the factory. The cleaning procedure (every 25-50k miles) is to wash and then re-oil the filter. It’s ready to go out of the box, and it’s definitely a great buy.

  17. Ralph says:

    Thanks once again Jason. I still plan on doing at cold air intake, but will try to hold off and felt this is a descent compromise for now ( and much easier to explain to the wife! ).

    By the way after my last visit to the dealership with regards to the gas pedal recall issue the shop foreman said that he had no problem with the “charcoal filter removal” . He said it was there to help control emissions, but that it would not; a) void warranty b) cause a failed vehicle emission inspection c) cause any damage to the engine.

    I plan on doing both, k&n & charcoal delete tomorrow.

  18. Rob says:

    I have a 2003 toyota tundra w/the 4.7. I installed the k&n air filter and I was very pleased with the results of the throttle response and horsepower that I gained.

  19. Jason says:

    Ralph – Great – do you think the throttle response is better?

    Rob – Thanks for your comments man – if you feel like leaving a review of the filter here I would be very grateful: http://www.tundraheadquarters......air-filter

  20. Ralph says:

    Jason-I did the modification on Friday. So far, it seems that truck is much more responsive and lively. It appears that it is breathing easier. Not sure if it is directly related the the k & n or the charcoal screen delete, but definetely the combanation seems to have improved the intake some. I still assume a CAI system would make my truck more responsive with a slight hp gain and at least another mpg +.

    I will try to observe over the next few weeks and let you know if I experience any mpg increase with current mod.

  21. I can’t say I agree with your results. I tried the K&N filter for my 4.6L and have lost over 1.5MPG on average and in some driving conditions such as freeway driving have lost 3.6MPG. Really not happy with the filter. Also I have a wierd hesitation when starting from a complete stop. Dealership can’t explain it at all no warning lights but if I take out the filter 100 miles after putting in the stock filter the problem just goes away. I bought the filter based on the information from this site and couldn’t be more unsatisfied with the result. I don’t know if it is just how the 4.6L reacts or if my truck is just strange.

    • Jason says:

      Robbie – That is definitely odd. At worst, the filter should have no impact. Any other 2010 4.6 Tundra owners with similar problems?

  22. Mark says:

    Responding to Carl regarding that filter:

    I know the filter you are talking about up past the OEM filter. I noticed it today. I have a 2009 5.7 Tundra and it’s in there. The OEM filter is a cotton type fiber and I’m not sure what they other filter is for. Perhaps this helps with filtering the air even more and reducing noise?

  23. Jason says:

    Mark – Interesting. I’ll see what I can find out – should have done that when I read Carl’s response, but I sort of forgot about it.

  24. Robbie says:

    Dealer say’s it’s not the filter and it wouldn’t affect it in any way. Problem started in conjunction with pedal recall fix both filter and fix done within 50 miles of eachother. Dealer had factory rep do ride-a-long with computer hooked up and have had problems since about 3000 miles. Factory rep is having Toyota engineers look at problem and see what may be going wrong. Please see coments made on 4.6L topic concerning same. Unfortunately factory rep said truck is having problems and there are a few others out there with the same issue. Which helped because I was feeling a bit left in the dark and alone with this issue. Also to help matters out it happens randomly so when dealer is looking at it the problem may or may not occur. The best thing is that the dealer is awesome and told me just to swing by when it is happening so they can see what is going on. This has been a big help as they know I’m not making things up. Just wish the problem were fixed, and I could cross an intersection without waiting for all traffic to be 2 miles away because I don’t have any idea when I push on the gas pedal if the truck will go really slow for a few seconds, or just get up and go.
    If you have any ideas please share them with the Toyota engineers because the check engine light never comes on when it does this.

  25. DP says:

    Just a quick note to all regarding mpg loss after install. If you disconnect the battery, the transmission and computer reset to factory defaults, and the “learning” begins again for driving patterns. Generally between 500-1000 miles all is settled and the milage should be much better.

  26. bugatti123 says:

    Hey just a quick question regarding rumors I heard about the drop in K&N air filter.

    1. Rumors about people with Tundras hearing a whistle sound at idle
    2. Rumors that the lid on the filter box cannot close and the filter has to run open box without a lid

    Also, what is the TRD drop in filter? is that the one that has all of the TRD logos on the filter box and stuff? How does it stack up to the K&N and how much is it?

    Any feedback would be greatly appreciated. Thanks!

  27. Jason (Admin) says:

    bugatti123 – Never heard that the lid won’t close correctly with a new K&N. However, the new filter is definitely louder.

    A whistling sound could be the result of a bad seal around the lid, but the term “whistle” means different things to different people. At wide-open-throttle, it’s definitely louder than stock…but that’s part of the reason it works.

    As far as TRD drop-in vs. K&N, they’re the same design and operate under the same principle. I wouldn’t mess with the TRD version because it’s more expensive.

  28. stew says:

    I have 2003 tundra trd(stock) and have added a K&N filter and have no real comp;aints,but for some reason at a low RPM if I punch throttle there is a hesitation before accelorating.Is there a fix for this

  29. Jason (Admin) says:

    Stew – The filter wouldn’t cause throttle hesitation, so I’d guess it’s something else.

  30. D. Rod. says:

    I installed the K&N Cold air intake on my ’08 Tundra. On one hand, the sound is great. On the other, I have actually lost gas mileage and I have combination of warning lights on my instrument panel that is associated with the mass air flow sensor. It seems that that several others are also having this same problem. Toyota nor K&N have a remedy for this.

  31. Charlie O. says:

    I installed the K & N filter on my volvo s60 and Lexus RX300
    and noticed right away a responsive acceleration on the vehicle, but don’t know if there is any gas mileage saved. I placed a blue fiber filter above the box air flow port with a wire mesh above it before the k & n filter to absorb any dirt before reaching primary filter (k & n ) and prevent reaching the MAF sensor. There is no hesitation when I step on the gas pedal. Highly recommend K & N filters.

  32. Jason (Admin) says:

    D. Rod – If the K&N filter you install was oiled at the factory, it shouldn’t cause any MAF sensor problems. However, if you or your mechanic oiled it themselves, there’s a much higher likelihood of a problem. Too much oil on the filter can damage the MAF.

    Charlie O – Glad to hear it. K&N is just one company that sells this kind of filter, but from our testing they’re definitely worth consideration.

  33. 504Ed says:

    The filter that looks like it riveted in place on the underside of the air box cover is called a hydrocarbon filter.

  34. Tundra shooter says:

    I am going to buy a K&N filter for my 2011 5.7 Tundra. The best place I have found to buy K&N is AJUSA.com. I have bought there before and they charge for shipping but even with shipping they are the best price around!! Thanks for the reviews. They helped with questions I had.

  35. M. Wildman says:

    I replaced the drop in filter with a K&N filter about 9 months ago. Slight sound difference and I gained about a mile more per gallon; which comes to about 25-26 more miles per tank of gas. Well worth it and I don’t need to change the filter for a long time.

  36. Gabe says:

    You should go to eBay for your k&n filter. They are the cheapest around. $37 and free shipping!

  37. jim says:

    Bought an Airaid cold air intake for my 07 Tundra 5.7 V/8 and then put it on the 2010 with no problems and sounds great when you punch it. They only thing i did was buy a spare filter which is a pricey but you swap the dirty one out and the spare goes in and then clean the dirty one and oil it and it is ready for the next change. This way you are not waiting several hours for it to dry and then you have to add the oil.

  38. Larry says:

    Explain something to me please. How does an air filter improve milage?????

    If the filter is clogged, then less air gets to the manifold and the pressure is lower. The result of lower manifold pressure is less fuel injector duration AKA less power because of less fuel being injected because there isn’t enough O2 getting in for a full load of fuel.

    The only thing an air filter can do is keep dust out of the engine but it can’t improve milage. If it clogs they you lose power by using less fuel. You get the load to it’s destination but at a slower speed.

    While there may be a difference in milage it won’t be enough to even pay for a cool looking filter.

    People, apply some technical thinking and science of combustion.

  39. Julian says:

    i have a 2013 Tacoma V6 TRD. Do you know what makes of CAI will void the warranty?

  40. Ed Anderson says:

    Thanks for the tip on removing the hydrocarbon filter under the air filter box lid. I have a K&N cold air intake that uses the stock air box with a K&N filter. It works great now on my’06 Tundra Limited crew cab with a 4.7 V8.

  41. joe gray says:

    I put K&N on my 2012 tundra and sounds great but lost low end power. It acts like its getting to much air now and not enough gas?

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