I have been reading in a few places that air filters get better with age, is this true? And how much better?

Would it have any effect on quality of the oil or make oil dirty faster?

Or is there not a great deal of difference between new and used filters?

Thank you for your time.


7 Answers 7


I don't have any empirical evidence for this, but would say no for two reasons:

  • An air filter will collect more dust, dirt, and debris until it gets so full that it starts pushing the older dust, dirt, and debris through the filter, which is what you are trying to prevent in the first place.
  • As the air filter collects more dust, dirt, and debris, the filter element becomes more restricted causing less air to flow into the engine, hurting performance and fuel mileage.

A dirty filter will not make oil dirtier faster, but as it gets so full and the dust, dirt, and debris (hereafter called "stuff") starts pushing its way into the intake tract, it will cause buildup inside the engine. The "stuff" will get into the engine combustion chamber and create excess wear on all the moving parts. There is basically no way for the "stuff" to get into the oil. Oil gets dirty usually from cleaning excess hydrocarbons off of working parts and from the oil itself breaking down due to heat and age.

As far as the difference between new and old filter, a new filter will clean the air: an old filter won't do such a good job.

  • A good answer I would also say the same. I would like to think that manufacturers make the filter to perform at its best from new and that anything after that would be worse. How often do you personally change your filters? I know everyone has their own opinions on when it should be done but I like to get a wide range of opinions before I make mine.
    – ceefax12
    Feb 27, 2016 at 23:16

It all depends on what you mean by getting better.

It is possible that, as the very small holes in the filter that let air through start to trap particles, the places where air can get through will get smaller and smaller. Therefore the filter will start to trap smaller and smaller particles. The air filter may get more efficient at filtering, but it will also start letting less and less air through for the engine to breath.

Some fine particles that get into the engine may possible get passed the piston rings into the oil and make the oil dirty, but the majority of dirt in the oil will be combustion soot that gets past the piston rings.

  • Another good answer, it's only logical to think that it would get better as it gets blocked but with a trade-off that the engine will struggle for breath. And I was also thinking that any dirt that does get burnt will stick to the bores of the engine and get wiped away by the piston rings which have contact with oil will make it dirty. How often do you change your filter? I know everyone has opinions but I’d like to hear yours
    – ceefax12
    Feb 27, 2016 at 23:17
  • @ceefax12 I don't generally have a schedule, I just check it now an then. I generally change the oil at the same time each year, but I won't have done the miles which would require a service.
    – HandyHowie
    Feb 28, 2016 at 13:25
  • ahhh right I see, I was going to go with a 15k miles change because I do a lot of miles, I would easily rack that up within a year. Do you think this is too soon?
    – ceefax12
    Feb 28, 2016 at 14:08

The function any filter is to remove small particals. In an air filter,the air is purified form dust particals before entering in to carburattor for mixing of fuel with air. So if tha filter is already full of dust its efficiency to clean the air us reduced and also there would be a blockage in tha air passage . Hence aged filter does not leads any betterment to the vehicle.


If you are discussing paper or cardboard air filters for the engine they degrade overtime and have to be changed. Oil filters are suggested to be changed with every oil change. There are generally two types of air filters a Cabin air filter and a engine air filter.

It is better in the long run to get a reusable air filter that can be washed and re-oiled to trap dirt and dust better.

Older vehicles like ones with carburetors that had air-filters that were round or oval shaped would get poor fuel economy due to dirty air filters.

Today dirty air filters do not really disturb fuel economy because of computer components. However, engine performance is changed with a dirty air filter regardless of the autos age.


I have been reading in a few places that air filters get better with age, is this true? And how much better?

No, not for any reasonable definition of "better."

Think about what an air filter is designed to do: stop all particles that are larger than some known cross-section (often measured in microns). Anything smaller than that value will be trapped by the filter and unable to proceed.

Let's use an extreme example: you've covered your air filter in fine gravel (e.g., from a fish tank). Clearly, this is now an "aged" filter that has prevented a bunch of nonsense from passing it.

However, you haven't increased the net filtering capability of this mess in any significant way. Remember, a filter is supposed to pass everything smaller than a specific cross-section. However, you haven't added a significant number of air channels that are smaller than that measure. As a result, the net effect is not something that's "better" at filtering out particulates.

What you've likely done, however, is plug the functional air channels that were present. A filter in the intake path of a functioning engine is effectively a vacuum sucking those particulates against its air channels. If you intentionally add a bunch of mess to the filter, you'll plug those air channels. The result is less air getting to the engine which is combined with less fuel and resulting in less performance.

So, if your goal is equal or better engine performance while running on ever better intake air quality due to a nasty old air filter, it's not possible. You can use a dirty air filter to progressively strangle an engine over time but I doubt that's anyone's definition of "better."


Tested the "air filters get better with age" theory on a vacuum cleaner, and as expected it performed best with clean filter bags, and the dirtier filter bags were prone to cracks and tears and when even there were no visible cracks dust particles could be seen on the secondary filter.
So I think same should happen with car air filters too,the only difference would be the scale of the filter size and the amount of dust gets into the air-intake. So my answer would be new is always better, but you can clean your air filters after they get dirty with air to lengthen its life, or I have seen some high performance washable air filters in the market (car specific) and one can test those out.
A new filter will always do a better job of cleaning the air.


I think you might be referring to the K&N cotton and oil air filters. They claim that as the filter collects dust particles, those particles actually help keep smaller particles out.

If you can weed through the marketing hype, this link explains a lot of what they say.

From the article:

"As the filter begins to collect debris, an additional form of filter action begins to take place because air must first pass through the dirt particles trapped on the surface. That means a K&N air filter continues to exhibit high air flow throughout the life of the filter while it is accumulating dirt. At the same time, the air flow for an average paper air filter can decrease dramatically as the paper element gets dirty. So as dirt accumulates, the performance advantages of a K&N air filter can increase! Tests performed by an independent laboratory commonly known as the Frazier Permeability Test have shown that the Medium used in K&N air filters flows more than 300% more air than paper air filter medium when compared on a square inch per square inch basis"

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