11 myths about air filters: expose them all!

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The first cars lived without filters at all. They didn’t care about the service life – they just wanted to run. Nowadays not a single automobile manufacturer does without filters. Since it is necessary to periodically change filters, it is inevitable that there is a discussion about whether it is necessary to do it or not. Let’s get to the bottom of the major filtration myths.

  1. The oil filter in the engine is more important than the air filter.Not at all. Each filter has its own job – that’s right. The difference is that an oil filter works within the confined space of an engine where outside dirt and abrasive particles do not get in, and the air filter stands in the way of everything that can get with the air into the cylinders and further with the oil washing the cylinder walls into the system. Unlike oil filters, through which contaminated oil can pass many times during the cleaning process, the air filter must unmistakably remove dangerous contaminants once and for all.The word “filter” comes from Rome: filtrum is “felt” in Latin. The Romans used compacted sheep’s wool to clean wine, water, and olive oil.
    In modern cars, you won’t find either sand or felt filters, the main filter element is paper.
  2. All filters are made from the same filter paper. So why buy expensive?Few people make real filter paper. The best-known manufacturers are Ahlstrom and Neenah Gessner. But each filter manufacturer makes its own adjustments to the filter element, depending on the peculiarities of this or that engine. Some add synthetic fiber, while others add paper made of special wood. The fiber manufacturer does not disclose the technology to other manufacturers. Cheap filters, on the other hand, are made with low-grade base grades of filter paper.
  3. An expensive filter can be replaced with a cheap one that just needs to be replaced more often.This is one of the most dangerous misconceptions: Do not confuse “service life” and “filtration parameters”. They are not the same thing. Cheap air filters as passed particles twice or even three times bigger, than it is required by automobile plant, so they will pass them, no matter how often you change filters! Therefore installation of two, three, or even four cheap filters for short intervals is not equal to the installation of one authorized filter for the whole service interval.
  4. All air filters are the same, you just have to find the right size.Yes, all filters are the same in principle, but they differ from one another in how well they do their job. Air filters are made for a specific engine type, based on engine specifications, service intervals and position under the hood. For each engine and vehicle model, a filter is made according to the manufacturer’s specifications, which also determines the interchangeability of the filters. So, external similarity does not mean total equality.
  5. You can tell when you need to replace the filter by the way it looks. Alas, that is not true. You cannot determine the threshold for replacing the filter by sight, smell, sound or touch. The only criterion is the service life in kilometers, specified by the car manufacturer. Adjusted, again, by the factory, for operation in severe and dusty conditions.
  6. The air filter of a famous company is expensive but cleans no better than a cheap one. Assertion of amateurs. Firstly, it is impossible to check the degree of purification independently, without instruments. Secondly, none of the car manufacturers installs cheap filters from unknown companies. No one wants to take a risk, when it comes to such a responsible and expensive part of a car, like an engine. Thirdly, only filters from authorized manufacturers provide the necessary degree of purification because they were created at the request of car manufacturers. Finally, quality can’t come cheap.
  7. 7. The air filter can be repaired by blowing it out and continue to be used on the vehicle. It is true that by blowing, the filter is cleaned. But only as if. In fact, only the coarsest impurities on the outside of it are removed. The fact is that modern automobile filters work on the principle of depth filtration. There, in the depth of the filtering material, the finest cleaning takes place. Therefore, no blowing will restore the parameters of the filter, which is about to be replaced.
  8. The fuel economy of the engine is not affected by the air filter, but only the air mass flow sensor.
    This is one of the major myths about filters. The main element of the MFR sensor is a noble metal wire which is energized. It heats up and cools down more or less depending on the air flowing around it. A change in temperature causes a change in its resistance. Depending on this the control signal about the amount of air flowing into the engine is generated.The RTD sensor needs clean air, which only a good filter can provide. A cheap filter leaks contaminants which, once deposited on the wire, interfere with the heat transfer and the control unit receives distorted information. MANN+HUMMEL calculates that an error leads to 3-5% higher fuel consumption.
  9. Quality filters are too expensive because these companies have large marketing budgets.Yes, quality filters such as Fram, K&N, Bosch, MANN are quite expensive, because today they are some of the best and highest quality filters for a car. When you buy top brand filters, you are basically paying for a quality part.
  10. Cabin filters can only screen out dust and still allow smaller particles like plant pollen through.Among all car filters, the cabin filter has the highest degree of filtration. On average, it starts working from particles’ size of 0,5 microns (for comparison, the thickness of a human hair is 70 microns). This is the size of plant pollen and many viruses. So installing a quality cabin filter can put a barrier to allergies and other diseases.
  11. The car filter does not use chemical air purification. In fact, both chemical and electrostatic methods are used to combat cleanliness. Quality cabin filters have an antibacterial impregnation that prevents the growth of microorganisms, fungi, and mold on the filter element. The duration of the impregnation is limited, so the cabin filters must be replaced annually.As for electrostatics, this is the way to trap particles virtually at the molecular level. The filter attracts them to itself and keeps them out of the cabin.


David West
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