• May 7, 2009

Dear Tom,

I own a 2006 Chevy Impala and I change the oil and filter every 3,000 miles. How often should I change my air filter?

Jack from Saginaw, MI

Jack,

According to GM's normal maintenance schedule, the air filter should be replaced arbitrarily every 60,000 miles whether it needs it or not. However, I replace it every two (2) years or 24,000 miles, whichever comes first. I base my recommendation on the environment in which I drive my vehicles. Summer construction, which cranks up around here in April and goes until September, creates a lot of dust, dirt, and road grime that gets into the air filter. I inspect it every oil change just to make sure it's clean and allowing good, strong airflow to the engine.

Jack asks a great question. The air filter is out of sight (packed tightly inside an enclosed air intake case) and therefore out of mind. This critical member of the performance system requires careful attention if the engine is to operate at peak performance and deliver maximum fuel efficiency. The air filter screens out harmful dirt and grime that would otherwise find its way into the engine. This grit can and does cause internal engine wear. It can score cylinder walls and stick to close-tolerance mating surfaces, and cause bearing and lubricating surface wear. Carmakers suggest keeping a close eye on the air filter; hence their recommendation of aggressive inspection every 6,000 miles.

What To Look For

Check your filter at every oil change
Look for visible soot or dirt on filter
Replace according to your owner's manual, or more often if you're finding your filter picks up a lot of dirt

In addition, it's important to realize that computer-controlled fuel injection relies on a clean air filter to maintain the delicate balance of air: fuel ratio fed into the engine. If the air filter is dirty, then the fuel delivery system goes haywire trying to maintain a balance of air: fuel. The ECM (Engine Control Module) aggressively adjusts fuel mixture in its attempt to compensate for the reduced airflow. This results in incorrect air: fuel ratios and hence inefficient combustion, poor fuel economy, and overall poor performance. And all because of a dirty air filter. Ouch, that's costly! Remember, good airflow is paramount to proper engine operation. Your car's engine is a giant air pump. When air is pumped through it efficiently your car performs better and gets better fuel mileage.

When replacing an air filter, always use OEM (original equipment) or better. Companies such as K&N and others make high flow air filters that last for the life of the vehicle. For instance, K&N's "Million Mile Air Filter" is warranted to last for a million miles with proper maintenance. Made out of cotton within a rubber casing, the K&N filter is can be removed at regular intervals for cleaning and oiling, than reinstalled.

On vehicles equipped with carburetors, a dirty air filter causes the carburetor to dump raw fuel into the engine. This results in poor fuel mileage, drivability problems, and a plugged catalytic converter (more gas is dumped into the engine than the cat can process). The rock of carbon that forms inside the cat restricts exhaust flow, decreasing performance and engine power. All this trouble due to a dirty little filter! As you can see, keeping a clean air filter will definitely save you money.

Read More:

- Oil Change Every 3,000 Miles?
- Why Do My Brakes Squeal?
- Synthetic Motor Oil: Should You Use It?



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