Horsepower and fuel economy are two terms that don’t usually go together. Like good looking AND smart. But every now and then, life cuts us a break and let’s us have our cake, and eat it too.
Your engine needs oxygen in order to combust fuel. So it draws fresh air into the cylinders, through the intake manifold. Then the fuel injectors spray fuel in, and the spark plug ignites the mixture. Without oxygen, fuel is just another liquid.
Before air can rendezvous with the go-juice, it must first pass through the air filter, which is mounted at the very tip of the air intake system. This air filter’s job is to remove any dirt & debris that might try to get into the engine. After all, sand and dead bugs aren’t exactly combustible.
This air filter is made from a thick paper, which is folded like an accordion. It sits inside a device called the airbox, which usually has a tiny hole at the bottom to allow air to pass through the air filter. Problem is, a stock air filter is like stuffing the Sunday Times into a snorkel, then asking your car to breathe through it.
It can be done, but your engine has to work pretty hard in order to breathe. Sort of like if you went snorkeling over a coral reef, and instead of using a nice big snorkel to breathe, you used the straw from your Big Gulp. You’d swim 10 feet, and be out of breath.
A performance air intake (like a K&N air filter) is made from a cotton gauze material, which is treated with a special blend of oil. This “filter media” is much more breathable than paper, so more air is allowed through. To better understand the difference, hold a piece of newspaper over your mouth and take a breath, then pull your shirt up over your mouth and take a breath. See the difference?
With the cotton gauze performance air filter, more air gets to the engine, and more contaminants get removed from the air. Those sticky oil-soaked cotton fibers attract the dirt particles from the air like a magnet, keeping more dirt out of the engine, while increasing the airflow.
When fuel is combusted inside the cylinder, some of that fuel can actually go unburned. However, when you introduce more air into the equation, you get a higher burn rate, which reduces the amount of unburned fuel. This translates into more power being produced from the same amount of fuel.
The reason that a performance air filter can help you get better gas mileage is because it’s going to require less fuel to create power. Since your engine is combusting more of the fuel, it’s going to require less fuel to propel you at the same speed.
So, if you can avoid the temptation to prod those extra ponies with your right foot, you can usually squeeze an extra 1-2 MPG’s out of that new performance air filter. Plus, most performance air filters are reusable, so you won’t have to buy another one as long as you own the vehicle.