Ask Car Mechanic

Ask Car Mechanic

How To Fix It

When Should You Replace The Engine Air Filter?


When Should You Replace The Engine Air Filter?

An air filter is a part that is essential for normal engine operation. In this article, we will tell you why it is necessary to change the engine air filter, how often you should do it, and also give some useful tips. This information will help not only beginners but also experienced car owners.

Why Do You Need An Air Filter?

The combustion chamber of the vehicle engine must be fed with the fuel-air mixture continuously during operation. The air is sucked in from the environment and then sent to the air filter which cleans it from dust, soot, dirt, insects, plant seeds, and small particles of rubber.

For the fuel-air mixture to burn completely, the air in the mixture must be 15-20 times larger than the fuel. Therefore, a car consumes from 100 to 250 cubic meters of atmospheric air per hundred kilometers. If it is not well filtered out, the particles of dust and dirt will get inside the engine, which will worsen its performance and eventually lead to premature failure.

The more the air filter is clogged, the stronger its resistance to airflow. This leads to over-enrichment of the mixture with fuel, and, consequently, to its incomplete combustion. Thus, the total fuel consumption increases. The toxicity of exhaust gases also increases.

What Happens If You Don’t Replace The Air Filter

If you think your air filter is dirty you should always do a visual inspection first, but just in case you wanted to know what will happen if you don’t clean the air filter, here’s what:

1. Engine Power Loss

The explanation is simple, the cleaner the filter, the less power it needs to suck air through it. if the filter is dirty, dirt, dust, and other micro-particles can get through the filter, which can cause scratches and minor damage to the cylinders. If not replaced, the air filter must at least be vacuumed of dirt and dust.

2. Increased Fuel Consumption

Fuel consumption increases proportionally. If the engine constantly lacks a certain amount of air, it uses more fuel. The more powerful the engine, the greater the fuel consumption, often a difference of 2-3 liters.

On average, you need to change the filter after 30-50 thousand kilometers of mileage, or 10-20 thousand kilometers if you drive on rural roads.

3. Unstable Engine Idling

Another indication that it is time to change or clean the air filter is unstable engine idling. In a well-tuned engine (without any problems) the engine runs clean, even and stable. 

If the filter is clogged or does not allow air to pass at all, the engine starts to work in jerks, sometimes it can completely stall. The explanation is simple,  the engine does not have enough air to function properly.

4. Engine Problems

Alternatively, in the case of a dirty air filter, two symptoms may appear, with very unpleasant consequences. The first is starting the engine, the engine will react sluggishly, especially in cold seasons. The car will start after a second or third attempt. As a result, such an engine start will have a bad effect on the battery and the starter as well.

The second symptom is that the engine is constantly flooding with fuel. Lack of clean air supply leads to a constant intake of fuel from the system. Due to the lack of ignition, fuel accumulates in the cylinders, but the consequences are unpredictable.

5. Engine Knocking

This is the least probable cause. It is the most extreme case when you don’t even check the air filter at all, although it is more common on cars with a carburetor (really old cars). 

The consequences can be terrifying for the engine:

  • Burned-out cylinder head gasket 
  • Burned-out cylinders 
  • Burned-out oil scraper rings
  • Missing valves.

When Should You Replace The Engine Air Filter?

Photo By

The mechanics usually combine air filter replacement with scheduled engine oil replacement, which is done after 10 or 15 thousand kilometres (depending on warranty conditions).  it directly depends on the condition of the car. Mileage is not an indication for replacement.

The air filters of those cars, which are used on dusty roads, as well as in constant traffic jams in a polluted metropolis, are the most polluted. In such conditions, the air filter should be changed sometimes even more often than a planned oil change.

Whether it is time to change the air filter can be easily determined by visual inspection. To do this, you just need to unscrew (or remove the latch) the lid of the air intake, pull out the filter and inspect it.

If the filter element is relatively clean, you can continue driving. But if it is grey, and its honeycomb is clogged with dust and all kinds of garbage (insects, poplar down, etc.), then it is time to change the filter,  the sooner the better. Anyone, even a child, can distinguish between a clean filter and a dirty one.

Diesel engines (especially turbocharged) are more demanding for the quality of the air entering the combustion chamber. Therefore, owners of such machines need to be especially careful to monitor the condition of the air filter and change it in time.

Some simply blow or vacuum the air filter and then continue to use it. It’s not worth doing. It is not such an expensive element that you can save on it.

Leave a Comment