The function of an air filter is to filter out suspended particulate matter entering the cylinder air, in order to reduce wear between the cylinder and the piston and piston rings. Among the three media required for engine operation, air consumption is the highest and comes from the atmosphere. If the air filter cannot effectively remove suspended particulate matter in the air, it can accelerate the wear of the cylinder, piston, and piston ring in light cases, and cause cylinder strain in heavy cases, shortening the service life of the engine.
 
1. Misunderstanding of usage
1) Quality is not required when purchasing. Due to some maintenance personnel not having a correct understanding of the importance of air filters, they only purchased them for cheapness and did not demand quality, resulting in abnormal engine performance shortly after installation. Especially in the automotive parts market, where there are many counterfeit and inferior products, when purchasing, we should compare our products with other suppliers and adhere to the principle of quality first.
2) Remove it randomly during use. There is scientific evidence that engines must use air filters. However, some drivers arbitrarily remove the air filter, allowing the engine to directly suck in unfiltered air. The test of removing the air filter on a truck shows that after removing the air filter, the wear of the engine cylinder increases by 8 times, the wear of the piston increases by 3 times, and the wear of the piston ring increases by 9 times.
3) Maintenance and replacement are not based on reality. In the accompanying user manual, although it is specified that mileage or working hours are used as maintenance or replacement data. But in fact, the maintenance and replacement cycle of air filters is also related to environmental factors. For cars that frequently drive in dusty environments, the maintenance or replacement cycle of the air filter should be shorter; In environments with low dust content, the maintenance or replacement cycle of air filters can be appropriately extended. In practical work, many drivers and maintenance personnel mechanically follow regulations, rather than flexibly mastering them based on environmental factors. Maintenance is only carried out when the mileage meets the standard and the engine's working condition is clearly abnormal. It should be noted that maintenance at this time will not only irreparable the losses already caused, but also cause greater harm to the engine. Moreover, some drivers have no idea that the air filter will fail, and as long as the exterior is not damaged, they can continue to use it.

2. Identification method
How is the working condition of the air filter, and when maintenance or replacement is needed, the following methods can be used to identify it:
In theory, the service life and maintenance interval of air filters should be measured by the ratio of the gas flow rate passing through the filter element to the gas flow rate required by the engine. When the flow rate is greater than the flow rate, the filter operates normally; When the flow rate is equal to the flow rate, the filter should be maintained; When the flow rate is less than the flow rate, the filter cannot be used anymore, otherwise the engine's operating conditions will worsen and even fail to function properly.
When the filter element of the air filter is blocked by suspended particles to the extent that it cannot meet the air flow required for engine operation, the engine's operating state will be abnormal, such as a dull roar, slow acceleration (insufficient intake air pressure in the cylinder), weak operation (incomplete combustion due to rich mixture), relatively high water temperature (combustion still continues when entering the exhaust stroke), and increased exhaust smoke during acceleration. When these symptoms occur, it can be determined that the air filter is blocked, and the filter element should be removed in a timely manner for maintenance or replacement.
When maintaining the air filter element, attention should be paid to the color changes on the inner and outer surfaces of the element. After removing dust, if the outer surface of the filter paper has a clear natural color and the inner surface is bright, it can continue to be used; If the outer surface of the filter paper has lost its natural color or the inner surface has become dark, it must be replaced.