The function of the air filter is to remove the dust, carbon and debris before intaking the air mixed with the fuel. In this way, it can ensure a clean air intake. When the fuel is burned per volume, it needs about 10000 units of air to pass through the air filter. Even small particle can cause severe wear.
In general, it recommends to replace the air filter every 48000km. And also it needs to inspect it every 24000km.
The atmosphere contains three different densities particles, namely dust, residue and carbon. The dust content in highways is lower than that in rural and construction areas. In the dust concentration of the larger areas, we should inspect and replace the air filter frequency.
We should check the air filter when we replace the oil. Take the filter out and check the fold inside the depths carefully. Because sometimes the filter looks very clean from the outside, but in fact the internal has been very dirty. In this way, we have to replace the filter immediately.