One is for you, the other is for your car, truck or SUV. If they’re both doing their job, you and your car, truck or SUV can both take a deep sigh of relief, and a big breath of clean air. If they’re not up too par anymore, either of you could find yourself wheezing and coughing for a fresh breath. Who are they? One is an engine air filter. The other is your car, truck or SUV’s cabin filter.

They both do the same job; they filter the air. The air filter cleans the air that is pulled into the engine and used in the engine combustion process. The cabin filter cleans the air that fills the inside of your car, truck or SUV. This is the air that you breathe.

The air filter for the engine is essential. If it’s dirty, two things happen. One is that it restricts the flow of air into the engine. This is where the wheezing comes in. Your engine is fighting to take a deep breath when it should be concentrating on filling its lungs (cylinders) with a mixture of air and atomized fuel.

1. That mixture of air and fuel is essential in the 4-cycle process that occurs inside your engine. The 4-cycle process goes like this:
2. The crankshaft pulls the piston down drawing a mix of air and atomized fuel through the open intake valve.
3. The intake valve closes, and the crankshaft forces the piston back up into the cylinder and, in the process, compresses that volatile mix of air and fuel.
4. With both valves still closed, the spark plug creates a spark that ignites the air-fuel mixture. This shoves the piston back down the cylinder.
5. The crankshaft swings the piston back up into the cylinder with the exhaust valve open. The process drives the burnt air-fuel mixture out of the cylinder and prepares the engine for another deep breath of air and atomized fuel.

While a cabin filter cleans the air you breathe in the car, and an oil filter cleans your car's oil, an air filter cleans the air that your engine breathes.

If, during Step No. 1 above, the engine is struggling to bring in enough air, Steps No. 2 and 3 will not be as fulfilling for the engine. When the air-fuel mixture ignites it won’t create as much power.

The other problem with the engine air filter is that, if it’s dirty, some of that dirt will find its way through the filter. Then, those dirt particles find their way into the cylinders where they have a chance to operate as abrasives between the pistons, piston rings, and cylinder wall. Over time, they can score your cylinder walls and pistons. This can reduce the air-tight seal that is necessary to have the full and powerful effect when the spark plug ignites the air-fuel mixture.

The cabin filter filters the air that you and others in the car will breathe. It kind of goes without saying that it’s better to breath clean, filtered air than dirty air. The cabin filter cleans dust, pollen, dirt and other particles from the air that comes into the car from the A/C and heating vents.