Today I did the 30K mile service on my '06 Tacoma. I bought a Purolater air filter for it.

I bought the truck used with a little over 15K miles on it, so I had never changed the air filter. When I opened up the airbox, I discovered that the previous owner had apparently installed a K&N filter in it.

I almost considered returning the Purolater and buying a K&N cleaning and oiling kit, until I compared the two.

The Purolater actually has more filter element surface area, because the filter element looks to be about 3 times as deep. The K&N did have more pleats, which does add surface area. However, it looked as if the extra pleats (maybe 8 or 10 more) weren't near enough to add enough surface area to make up for the extra depth of the Purolater.

I don't know how the K&N made for other applications compares to other brands of filters for those applications, but this is my observation for my Tacoma.

So basically what I'm trying to say is that in this case, the Purolater looks like it would actually flow more than the K&N.

I had heard that one way the K&N increases flow is that it filters less. Something that I noticed with the last 2 K&N filters I owned is that there are pinhole sized holes in them. Hold one up to the sunlight if you don't believe me. The K&N that was in my Tacoma is the same way as the other two.

The Purolater filter has no pinholes. I checked it.

So the Purolater, which appears to have some sort of fiber material for the filter media, would filter better. That means longer engine life.

And it looks like the larger surface area of the Purolater would be enough to make up for the better filter media from a flow standpoint.

So tell me, other than being reusable, where is the advantage of a K&N for my Tacoma? I see none.

There's anothing I wonder about. I had read in other threads about the secondary air filter. Today was the first time I saw it. With the K&N letting in more dirt, and the potential for oil mist from the K&N being sucked in, I wonder if the K&N has caused the secondary filter to get dirty. It looked okay, but then again I didn't remove it and look at it closer.

I'm going to keep it like it is for now and compare power to the K&N. Later on I might remove the secondary filter, because I wouldn't want to have it in there if it's dirty because of the K&N. I'll post later on my findings.

 

I installed a K&N air filter in my 03' Tundra to see if it would increase the power or mpg like they claim. It did help by increasing about 1.5 mpg, but didn't notice a power increase. I was getting 12-14 MPG, and now get 14-16.

 

Everybody has their filter favs but I've never read any solid truth to any aftermarket filter reducing engine life. I'm sure if K&Ns were as bad as people assume they wouldn't be in business.

I ran one on my turboed Eclipse where their is near zero clearance between the the turbo's vanes and the housing and it filtered fine but my Eclipse was also a summer only street vehicle.
On my Runner I prefer a simple paper filter since I do think they filter better and when off road that is important to me.

 

K&N got where they are now because of the publicity from racers using them. But then again, racers rebuild their engines on a regular basis. The increased wear a street engine might see may not be significant enough to have caused lawsuits. But I wouldn't want to take any chances.

All I do know is that I did see numerous pinholes through the filter media, and have seen the same holes with the last 2 K&Ns I owned.

I drove my truck today and noticed no power loss at all, so it appears that the K&N wasn't helping add power. The other K&Ns I had didn't help power either (or fuel economy).

Dave B., is it possible that fuel economy improved after breaking in and not from the filter change? Or is there anything else that could have explained the increase such as different weather conditions, a recent tune up, increased tire pressures, lower average speed, etc?

Assuming flow did actually improve, when more flow is sensed by the airflow sensor, the ECM has to add more fuel to keep the mixture the same.

And with normal driving, which is when the throttle plate is partially open, the throttle plate controls air flow by restricting it. So adding anything that has the ability to flow more is a moot point, since the flow will still be restricted by the throttle plate at part throttle.

So there would be no increase of anything with normal driving. It would still take the same amount of air flow (and fuel flow) to go a certain speed with a certain amount of load, and air flow is controlled by the throttle.

On a carburated engine, less restriction before the carb might reduce vacuum, which might reduce the amount of fuel that is sucked in, maybe increasing MPGs. On a fuel injected engine, this isn't the case.

There are some factors that can somewhat affect combustion efficiency (which affects MPGs) such as moisture in air or air temperatures, but the type of filter is irrelavant in this case.

I'm not doubting that your MPGs increased, assuming you measured correctly and used the exact same method for checking MPGs before and after the K&N. But what I am saying is that I don't believe the K&N was the reason why.

I believe that, at least for my application, a K&N is a waste of money, so I can't recommend it.

 

I ran the K&N on my Eclipse for 8 years and the three turbos I had on it never had any issues from anything getting past the filter and that was over 80k miles of driving and racing.

 

That's cool. But a vehicle driven on strictly on the street would also be less likely to have problems than a truck driven off road. I've been driving with a bunch of guys in a Florida national forest during a drought, when it was so dusty that I couldn't see the truck in front of me. I certainly wouldn't want a K&N in a situation like that.

My guess is that if you ran 2 identical engines for 10 years under identical conditions and for the same number of miles, one with a K&N and one with a stock filter, and then disassembled them and checked the cylinders, rings, and pistons, the one with the K&N would have more wear. This would be even more likely with a truck driven in dusty conditions.

That's not to say that the K&N equipped engine would need a rebuild. Many people don't keep a vehicle long enough for any increased wear to be an issue. But I would rather not take any chances.

 

Yeah,street is veyr different and I won't use a K&N off road and a simple paper one does me fine.

 

i wouldnt use a K&N on the street OR offroad. just personal preference. a filter with that many holes, and the size of those holes, cant be very good for the engine. the stock air box, while restrictive, does me just fine.