Sounds like BS to me… “In fact, those pin holes are what makes a K&N filter efficient. Within those holes, there are actually hundreds of microscopic fibers spanning them”
I have to think that if that was the case, we’d have a bunch of nearly transparent pre-oiled cotton disposable filters being used by OEMs. Instead, we uniformly get opaque or translucent dry paper filters, or possibly pre-oiled paper filters from both the manufacturers AND the vast majority of aftermarket makers like FRAM, Purolator, Mann, etc… Only K&N pushes this oiled gauze stuff, and basically claims that they know something that huge companies like Honeywell (parent of FRAM) don’t.
I went to rockauto.com and looked up air filters for a 2005 Jeep Grand Cherokee with a 3.7L V6 engine. The cheapest is $3.39 and the most expensive is $13.40.
They have the best prices and the best service of any online auto parts business I have ever used. They are the amazon of auto parts.
On topic, factor in the cost of K&N’s cleaning and re-oiling kit when deciding between them or paper.
I have been factoring in the cleaning kit – but you’re 100% correct, RockAuto is insanely cheap. We have a 2004 GC with the 4.0 inline six, but even those are really cheap on that site. At the local auto parts store, they are an easy $20. On RA, even the good name-brand filters like Wix and Mahle are in the $10-15 range.
I’m not a K&N zealot by any means, although I do have one on my project/weekend toy car. Same car also has modified exhaust, cams and remapped fuel injection.
The two parts of you statement that I disagree with are
(a) the idea that manufacturers would use oiled filter technology if it was actually better. As has been stated numerous times in this thread, manufacturers consistently make decisions with an eye on the bottom line. Just because a manufacturer uses a certain type or brand, does not mean its actually better. The most obvious example of this is tires. Unless you are $50k or more for your car, you can almost bet the tires on it are lowest bid items, not the best tires available for your car. Manufacturers also know that the average person who treats their car like an appliance isn’t going to maintain an oiled filter.
And (b) you will never win any argument about filtration by using FRAM as your chosen champion. Pretty widely noted by car enthusiasts as the lowest quality filtration product you can buy.
When I used to follow a used oil analysis / motor oil forum, there was a definite trend towards higher silicon levels in the oil of vehicles that used them.
That is to say, people who used K&N had more contamination from sand/etc making it past the filter.
The contamination wasn’t at dangerous levels, but it almost always be an extra 5-10 PPM.
I worked for Ford around 1980. The rule of thumb used to be:
Spend $1M overhead cost to save $0.25 variable cost, on a common engine part.
No doubt the ratio has changed since they sell fewer cars and more expensive ones, but there’s definitely still a strong motivation to save every penny they can on variable cost.
That rule was hard on the guys doing the engine processor coding, because not only did the cheaper sensors & actuators usually require more complex code, the guy making the decision looked better on his end while spending money in a different department. The result was always needing to stuff 5 lbs of code in a 10 lb bag. I was glad I wasn’t one of those guys!
But there is. Govt mandated fuel economy numbers are a bear to meet. If GM could add an extra .5MPG for $30, they do that whaaaaaay before throwing 10 times that for a lesser gain.
[QUOTE=DrDeth]
But there is. Govt mandated fuel economy numbers are a bear to meet. If GM could add an extra .5MPG for $30, they do that whaaaaaay before throwing 10 times that for a lesser gain.
[/QUOTE]
After they’ve done all of the free or nearly free things like taking 40 pounds of spare tire and jack out of the trunk and replacing it with a can of fix-a-flat, and removing two pounds worth of rear floor mats, and so on… If they thought they could fill tires with hydrogen to make them weigh an ounce or two less without exploding, I’m sure they’d try it.
There’ll only ever be niche markets for K&N filters as it’s so much easier to fit a paper filter. Domestic car OEMs will never fit them either - even if they weren’t more expensive - as the hassle of cleaning, drying and re-oiling isn’t a positive selling point.
That said, I’ve been using K&Ns for years and I think they’re great. I generally clean them every 2000 to 3000 miles, as it only costs a few pennies and an overnight wait for the thing to dry out. My current car has 206,000 miles on the clock (135,000 of which were with K&N filtration), and there’s no sign of filter oil deposits inside the airbox. That K&N filter has paid for itself many times over.
I find it very noticeable when the air filter is getting clogged (paper or cotton) as the engine’s power curve starts to get lumpy, making the gear changes less fluid and making the car lurch a bit when the throttle is lifted. As an observation, it seems that the filter performance is impaired if it looks grubby to the eye.
I have briefly run (non-ECU) cars with the air filter removed*, and there’s a distinct power boost. I reckon I get a couple of extra horses from a K&N filter compared to a stock paper type. It’s not a huge boost, but it does follow that a freer airflow is going to produce more power.
I don’t recommend this. Top Fuel dragster engines don’t have air filters, but then they’re stripped down and rebuilt every half a mile.
Amsoil filters do not require oiling for filtration but allow for better airflow.
I use one on my cold air intake. Combine this with a retune of the ECU to “teach” the computer to do with all the extra air it’s getting, and my butt dyno feels a definite increase in power.
I’d like to see actual dyno tests AND oil analyses showing that the HP/torque goes up, and that the internal engine wear doesn’t increase, before I’d consider a K&N.
Last I saw, HP/torque increased marginally, but the wear was noticeably higher (as measured by Si, Fe and other compounds in used motor oil).
You’re never going to see that. K&N results in higher silicon, which will result in higher iron/aluminum/etc readings.
There might be one wonky analysis that shows it, but I’ve seen a half dozen analyses that all showed K&N results in higher wear numbers and none that refuted it.
To elaborate on this with a specific hypothetical example:
-to cruise at 75 MPH, a car needs 40 horsepower from its engine. In stock condition, this requires the throttle plate to be opened to a particular position.
-We replace the stock air filter with a K&N filter that has less flow restriction. Now when we open the throttle plate to that same position, we get 40.1 horsepower from the engine.
-40.1 horsepower means we are cruising faster than we were with the stock engine. So we back off the accelerator pedal a smidge, and the throttle closes just a smidge, until the engine is making 40 horsepower just like it was in its stock configuration. In both cases, the total intake tract restriction, i.e. the sum of the throttle plate restriction and the air filter restriction, is identical, resulting in identical airflow and identical power output - and therefore identical fuel economies.
The ECU is of course paying attention to throttle position, but as long as the engine is operating in closed-loop mode, it’s watching the exhaust O2 sensor and adjusting the fuel injection rate so as to maintain ideal air/fuel ratio even when the throttle position is a fraction of a percent off of what it would have been in a fully stock engine configuration.
Exactly. Higher silicon and wear metals means that the K&N filters don’t filter as effectively as the standard paper filters.
I suppose it all comes down to whether or not one’s willing to trade off a slight increase in power for a measurable difference in internal engine wear due to ingested sand and other particles not stopped by the filter.
Makes sense for autocross or some sort of track car, but for a daily driver, it seems kind of dumb, if you ask me.
Of the nine filters they tested, here’s the highlights:
-the K&N had the worst filtration.
-the K&N had the second worst dirt capacity (before reaching the flow restriction limit).
-the K&N passed the second most dirt.
-the K&N had the lowest initial flow restriction (as noted upthread, the difference is tiny even at WOT, and irrelevant at any part-load condition, plus it clogs up more quickly than other filters, restricting air flow).
Check out the plots there for the details. Very informative.
OTOH, I’ve changed a lot of paper filters that had accumulated no more than a teaspoon of crud in 10-15,000 miles. This may be a case where the hard numbers don’t really matter and a moderate amount of filtration is for all practical purposes as good as “perfect” filtration.
I’d have to see studies where some small amount of hard particulates contributed significantly to an engine’s wear over its lifespan. I suspect that the damage caused by the small amount of extra grit from a K&N disappears into the noise floor.
Vehicles driven in very dusty, gritty, sandy or offroad conditions would be different, of course, but I suspect the wear issues would be proportional and “mostly” filtration would contribute as much protection as tight filtration.
Remember the glass sediment bowls on farm tractors? Then you had the oil bath between that glass & the intake to the carb.
Paper filters are very restrictive so they are way big to give good flow.
It is all about money…
Best insurance IMO is frequent oil changes. Sure, the oil has not broken down but it is DIRTY. People are just lazy and want it the easy way, not the best way.
From what I’ve been able to divine, the real determinant of internal engine wear due to contaminants isn’t so much the amount, as it’s the size of the particles.
For example, particles below a certain size (5 microns)just flow through the bearings in the oil without actually contacting anything, but larger ones actually catch and grind and cause wear, so long as they’re actually small enough to fit into the bearings in the first place (about 25 microns).
