Cabin Air Filter vs. Engine Air Filter: What’s the Difference?

Why Does the Engine Need an Air Filter?

The engine air filter traps dirt and dust, allowing only clean air to pass through. If dirt were to enter the engine, the grit could damage or scar sensitive components and increase the wear and tear on the engine. That can cause critical components to fail prematurely.

Older cars typically have a ring-shaped filter that surrounds the carburetor. Modern vehicles usually have a rectangular filter about the size of a paperback book in the car’s air intake. Others have an exposed cone-shaped air filter.

Cabin Filters for the Vehicle’s Occupants

With the advancements in air conditioning, some motorists seldom open their car windows and instead allow air to enter through the car’s heating, ventilation, and air conditioning (HVAC) system. Engineers realized that something should filter out harmful pollutants and dirt before the passengers breathe it in. Thus a cabin filter was created.

The cabin filter is a rectangular-shaped filter, often found behind the glove box in modern cars. There are four primary types of cabin air filters. As they get more complex, the price also rises.

• Fiber filter – The basic cabin air filter is a pleated fibrous material. It can trap most particles under three microns in size.
• Charcoal cabin filter – Embedded in the middle of the fibrous filter is a layer of charcoal that traps finer particulate materials. The charcoal also removes odors from smoke or exhaust fumes.
• Activated charcoal cabin filter – The filter’s charcoal layer can also use activated charcoal. Activated charcoal has been subjected to heat and chemicals to absorb gasses, and therefore odors, better.
• Electrostatic cabin filters – In these filters, the material holds a static charge. Instead of being trapped by fabric or charcoal as the fine particulates flow through, they are attracted to the electrostatically charged material and cling to it. This makes it easier to remove fine pollen and particles from the air.

Many cabin filters are advertised as being a high-efficiency particular air (HEPA) filter. HEPA is based on an international testing standard that requires manufacturers to meet certain air filtering criteria. Presently the standard allows for different grades of HEPA filters, but all HEPA filters should be stopping particles as small as .03 microns.

Engine Air Filter Types

Engine filters are generally made from one of two materials. Many filters use a paperlike fiber folded into accordion pleats for more surface area. This makes the filter more effective with a smaller footprint. Most paper filters are designed to be single-use; you replace them when they reach the end of their lifecycle.

Other engine filters are made from a gauze-like cloth with a light spray of oil on them to help trap particles. There are two main advantages to these filters: First, they can be removed, washed with detergent and water, reoiled, and reused. This eliminates waste and the expense of new air filters. Second, these filters often allow for more airflow than a paper filter, which is useful when a car is under full acceleration.

Occasionally you may see an air filter made with a spongy rubber foam. These are often used by dirt racers and off-roaders because they can be quickly washed out and reused after a race or a day in the sand. These filters are not practical for long-term use.

When to Replace the Filters

Check your owner’s manual for the recommended replacement intervals. If you often drive on dirt roads or off-road, you might need to replace filters sooner. Generally, a cabin filter needs replacing every two years or 24,000 miles. An engine air filter should be cleaned or replaced on that same schedule.

If you’re not sure when your filters were last changed, you can take the filter out and hold it up to a strong light. If the light is substantially blocked or you see caked-on dirt, it is time for a replacement.

Odors From Filters

Since cabin filters are designed to trap pollen, spores, and dirt, there is a chance that mold or mildew might develop over time. This causes a noticeable odor in the passenger compartment. Check your cabin filter if you notice a musty smell.

With some exceptions, most engine air and cabin filters are easy to replace. Take the time to locate them in your engine or behind your glovebox and grab a replacement from eBay Motors. When you install a fresh new air filter, you and your vehicle can breathe easier.