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Discussion Starter · #1 ·
So, K&N doesn't list an air filter for the Ascent yet, but the model they have says it fits pretty much every 2018 Subaru ... does Subaru use a standard sized air filter across all product lines so the K&N will fit the Ascent or do we need to wait for an Ascent specific model ya think?
 

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Can almost guarantee that this will do nothing but create a problem. Oil from filter tends to coat the MAF sensor and various other intake parts causing issues. Would recommend staying with stock. BTW, I am a huge mod guy, tuned my brand new S4 with 500 miles on it....
 

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Can almost guarantee that this will do nothing but create a problem. Oil from filter tends to coat the MAF sensor and various other intake parts causing issues. Would recommend staying with stock. BTW, I am a huge mod guy, tuned my brand new S4 with 500 miles on it....
Bludool- i coundn't agree more-K&N asking for trouble. The S4 could almost tune itself. What did you do a mild mapping.
 

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If anything, I'd go with an aFe oil-less filter. there's lots of debate over whether they are worth it over the paper filters since the "added horsepower" is usually just more airflow aka less filtration.

The reason I liked mine was it was easy to clean with compressed air and I didn't have to buy the paper ones anymore.

Given how cheap the OEM paper ones are for Subaru, that's not too shabby either.

(on my Tacoma)
 

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Discussion Starter · #5 · (Edited)
So, tone can be hard to gauge in post so let me start off by saying I intend no offense or snarkiness in what I'm about to say ...

Thanks for taking the time to respond but your response is inappropriate for what I asked. I asked if Subie uses a standard size for all air filters. I did not ask whether or not you think using a K&N is a good idea. Having used one for 7 years in an Outback, 4 in an Impreza and many years in 4 other makes, along with my brother doing the same, I've never had a single issue with K&N. I tend to get a little better gas mileage with them in fact.

Now, because someone may read this thread and get freaked out by your "almost guarantee" comment without any justification, let me explain why that comment is completely inaccurate.

1. K&N has sold over 10 million air filters. No company could sell that number of filters if they constantly caused engine damage. Your "almost guarantee" doesn't even pass basic logic

2. There have been no class action lawsuits against K&N for any damage caused by their air filters - there would be if your "almost guarantee" comment was even remotely true

3. I contacted my Subaru tech at my dealership just to verify what I already knew. He's worked there for decades, has worked on every model and is well versed in the turbos. He owns many Subies and even races them. He stated:
- He has no issues with new K&Ns and they don't cause any issues
- He has issues with owners not following instructions on cleaning their K&Ns
- Instructions state that you must allow the filter to air dry COMPLETELY
- Some owners wait an hour and then apply the oil. Keep in mind oil and water don't mix.
- They install the filter and drive off. Because oil and water don't mix, the airflow knocks the oil off the water soaked filter and the oil goes into your MAF, etc.
- This is NOT a problem with the filter. This is a problem with the owner who refuses to follow clear factory instructions on recharging the filter

4. Here is a scientific research paper comparing OEM with K&N: https://ac.els-cdn.com/S22120173163...t=1530315933_595b2edd821b11d0b0fbef3a1e7f7f92
Takeaways
- K&N is actually a little more restrictive with flow than OEM
- OEM filters better than K&N but researcher states that K&N would perform better in real world than how it was tested in research
- K&N gets better fuel mileage than OEM
- They did not test horsepower
- It's notable that the paper never mentions any chance of damage from using K&N

So why did I go through all this? Because it's irresponsible to make statements that are alarming and aren't backed up by facts. This is a forum where we all go looking for good advice. If you're going to make a statement like you can "almost guarantee" that using something is going to cause damage, then you need to back it up. I've backed up everything I've stated about the safety and performance of the K&N.

That all said, the filter for the Ascent is a different number than the one for the Outback on Subaru's site which likely means it's a different size. My tech also said that he runs OEM even in his STi, so that's given me some pause. I may or may not go K&N but regardless of the decision, it won't be because I'm afraid it's going to damage something.
 

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I was going to say earlier. The stock filter and intake systems on Subarus are good to 300HP. You don't need anything else unless you are building past this benchmark.
 

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Discussion Starter · #7 ·
I was going to say earlier. The stock filter and intake systems on Subarus are good to 300HP. You don't need anything else unless you are building past this benchmark.
No, I just like getting a little better mileage and touch better acceleration. I thought I was getting really good mileage with my Outback at 24.9 mpg at 126k but dealer said that's rather normal. If it was around 32, then he might credit the filter. So, I don't know. Probably won't upgrade it. Only getting around 19 now but I know it takes a while for it to settle and seal, so we'll see.
 

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Disclaimer:

I have the Subaru SPT POD and S-MAF tube on the 2006 and I have a hybrid I built myself that retains all of the factory dimensions on the other car. Neither car needs them, but I like the intake whoosh and BOV pops.
 

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So, tone can be hard to gauge in post so let me start off by saying I intend no offense or snarkiness in what I'm about to say ...

Thanks for taking the time to respond but your response is inappropriate for what I asked. I asked if Subie uses a standard size for all air filters. I did not ask whether or not you think using a K&N is a good idea. Having used one for 7 years in an Outback, 4 in an Impreza and many years in 4 other makes, along with my brother doing the same, I've never had a single issue with K&N. I tend to get a little better gas mileage with them in fact.

Now, because someone may read this thread and get freaked out by your "almost guarantee" comment without any justification, let me explain why that comment is completely inaccurate.

1. K&N has sold over 10 million air filters. No company could sell that number of filters if they constantly caused engine damage. Your "almost guarantee" doesn't even pass basic logic

2. There have been no class action lawsuits against K&N for any damage caused by their air filters - there would be if your "almost guarantee" comment was even remotely true

3. I contacted my Subaru tech at my dealership just to verify what I already knew. He's worked there for decades, has worked on every model and is well versed in the turbos. He owns many Subies and even races them. He stated:
- He has no issues with new K&Ns and they don't cause any issues
- He has issues with owners not following instructions on cleaning their K&Ns
- Instructions state that you must allow the filter to air dry COMPLETELY
- Some owners wait an hour and then apply the oil. Keep in mind oil and water don't mix.
- They install the filter and drive off. Because oil and water don't mix, the airflow knocks the oil off the water soaked filter and the oil goes into your MAF, etc.
- This is NOT a problem with the filter. This is a problem with the owner who refuses to follow clear factory instructions on recharging the filter

4. Here is a scientific research paper comparing OEM with K&N: https://ac.els-cdn.com/S22120173163...t=1530315933_595b2edd821b11d0b0fbef3a1e7f7f92
Takeaways
- K&N is actually a little more restrictive with flow than OEM
- OEM filters better than K&N but researcher states that K&N would perform better in real world than how it was tested in research
- K&N gets better fuel mileage than OEM
- They did not test horsepower
- It's notable that the paper never mentions any chance of damage from using K&N

So why did I go through all this? Because it's irresponsible to make statements that are alarming and aren't backed up by facts. This is a forum where we all go looking for good advice. If you're going to make a statement like you can "almost guarantee" that using something is going to cause damage, then you need to back it up. I've backed up everything I've stated about the safety and performance of the K&N.

That all said, the filter for the Ascent is a different number than the one for the Outback on Subaru's site which likely means it's a different size. My tech also said that he runs OEM even in his STi, so that's given me some pause. I may or may not go K&N but regardless of the decision, it won't be because I'm afraid it's going to damage something.


Forums are great for this, everybody loves to hate on stuff, even me. I ran across you post yesterday and even typed out a response lambasting K&N filters before thinking better of it and deleting it.


To the point, if your K&N fits in the air box and you are 100% sure that it is making a positive seal, use it. You seem smart enough to properly care for one of these filters, which of course makes all the difference in the world. Where people get in trouble with K&N is by not understanding that they require maintenance and inspection. As a mechanic, my opinion is to use a good paper filter and throw it away when it gets dirty.
 

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The stock filter and intake systems on Subarus are good to 300HP. You don't need anything else unless you are building past this benchmark.
...this, generally turbocharged Subarus don't like aftermarket filters w/o being turned for them. From I understand it can lead to a lean condition which causes damage over time. I'm running an AEM Dry Flow in my '12 LGT, but it's been tuned for in addition to the host of other modifications I'm running. Just my .02 though.
 

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I am amazed that NOBODY has even answered this man's question, amazing just amazing! Anyway the part number you looking for is K&N # 33-5064. It is the same air filter that is used in the 2017 Impreza. Also I would plan to remove the restricting carbon element as well. Plan on running a K&N once my Ascent comes in also. Been using K&Ns for over 10 years in my vehicles and have never have any issues.
 

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How would you know if the filter is causing issues?



Normally a cel will appear. The excess oil gets on the MAF sensor and it'll throw errors.


That being said, I used a k&n for a long time in my 2002 wrx without any issues. I think it's when the recharge kit gets used and most people use too much oil. To avoid any potential issues I never recharged the filter and just went back to the stock filter when it came time.
 

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Discussion Starter · #14 ·
I am amazed that NOBODY has even answered this man's question, amazing just amazing! Anyway the part number you looking for is K&N # 33-5064. It is the same air filter that is used in the 2017 Impreza. Also I would plan to remove the restricting carbon element as well. Plan on running a K&N once my Ascent comes in also. Been using K&Ns for over 10 years in my vehicles and have never have any issues.
Thanks John. Unfortunately K&N wrote me and told me that they do not have a product ready for the Ascent yet. While I would assume it's the same as the others, because Subaru themselves has the air filter as a different number than the Outback and the rest gives me some pause. I think I'll just run OEM until there is a K&N filter specifically for the Ascent or they roger up on 5064 working. How did you figure out it's the Impreza version?
 

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Discussion Starter · #15 ·
Normally a cel will appear. The excess oil gets on the MAF sensor and it'll throw errors.


That being said, I used a k&n for a long time in my 2002 wrx without any issues. I think it's when the recharge kit gets used and most people use too much oil. To avoid any potential issues I never recharged the filter and just went back to the stock filter when it came time.
Again, it's not using "too much" oil that's causing issues. It's not allowing the filter to dry completely before applying the oil. Adding oil to a wet filter and then blowing air through it leads to oil flying off as oil and water don't mix.
 

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K&N officially list the ascent as having a fitment. As posted earlier it is the same as the current gen Impreza. I am ordering one tonight.
Please let us know how it sounds/feels after you install it. At that price it’ll pay for itself in just 120,000 miles based on the 30,000 mi filter change interval. But if it makes the engine happy I’m all for it.
 

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Maybe I'm missing something about Air filter tech in the last twenty years... but I just go to the store, buy (usually) the cheapest of the 3 options given to me at my local O'Reilley's auto part store. Why do we/I want to add oil to it in the first place? All my cars are just factory, no special tuning etc...


Just wondering if I'm missing something!


Thanks
Dan
 

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Did the removal look like this https://www.youtube.com/watch?reload=9&v=Zp2XOihVZeA I running an AEM Dry. Had to reset the battery to clear codes the very first time I installed it.



I am amazed that NOBODY has even answered this man's question, amazing just amazing! Anyway the part number you looking for is K&N # 33-5064. It is the same air filter that is used in the 2017 Impreza. Also I would plan to remove the restricting carbon element as well. Plan on running a K&N once my Ascent comes in also. Been using K&Ns for over 10 years in my vehicles and have never have any issues.
 

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Do you know what the irony of worrying about how many fine particulates are removed by an air filter is?

We can put in a filter that removes particles down to micron sizes; Of course that engine would not be able to breathe through such a filter and it would be massive in size, like the size of the radiator.

It sounds great; lets filter out all of this stuff, the engine gets perfectly clean air, there isn't any pitting on the valve seats or cylinder walls.

Then we up and do two things that blows that all to h&!! ; We redirect the oily, gummy, watery, vapor-laden gunk out of the crankcase and loop it back in to the intake system through the PCV (positive crankcase ventilation) system. Also, we take some of the partially burned exhaust gases filled with soot, carbon and whatever now-cooked PCV goo and push that back in to the intake system through the EGR (exhaust gas recirculation) system.

Depending upon where the MAF (mass air flow) sensor is located in the intake duct we either spare it the oily, sooty goo but also throw-off the fuel mix by not accounting for the volume EGR/PCV feedback or we contaminate the heated element in the MAF by coating it with oil and soot. Its also imperfect because PCV vapors and EGR gases are at a much higher temperature (that costs us efficiency) and are not breathing air, instead being filled with partially combusted or even incombustible compounds (some stuff in oil does not burn).

Even if you put a K&N or any aftermarket air filter, or change the ducting around, you may improve the ability of the engine to suck in air but the ECU (engine control unit) may compensate that gain away through its own compensation. So you may not get the full benefit without a custom tune.

I just expect that the MAF is going to get contaminated so I use SeaFoam spray to periodically blast that clean and to maybe flood-out the engine until it stalls with SeaFoam and then let it sit to loosen up some of the carbon and soot on the intake valve stems. (a real problem with DI (direct injected) engines where there is not a wash of fuel/air mix on the inlet side of the intake valves to get off the PCV oil that has now turned in to molten tar and is mixed with soot from the EGR system.
 
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