This video is sponsored by MAHLE.

Air filters are a common replacement part, and many counter pros have sold hundreds or maybe even thousands of them during their career. But unlike your professional-installer customers, you probably only see a small percentage of the old filters when you’re selling replacement filters.

A dirty air filter can tell us about the environment it operates in, the frequency of regular maintenance intervals and, sometimes, the condition of the engine itself.

For example, oil in the air-filter element can be an indicator of PCV or piston-ring problems. Blow-by from the crankcase can work its way back through the intake system, being “recycled” along with the crankcase vapors. This oil can cause contamination of the mass airflow sensor. In the case of worn rings, it also can contaminate oxygen sensors.

Vehicle owners often are surprised to learn that mice, squirrels or chipmunks are the source of broken wires or some other electrical issue. But these critters also can cause damage to the air filter or airbox. In his experience, Dayton has seen nests built in airboxes and holes chewed through filter elements, and he once discovered most of a bag of dry dog food scattered throughout the airbox and engine compartment of a Trailblazer.

Here’s the bottom line: In the counter pro’s world of components and pieces, you still need to be aware of the bigger picture. Often, it’s not just one piece or part that solves a customer’s problem.  Instead, it’s a combination of proper diagnosis, thorough service and quality components that save the customer repeat trips to solve the same problem.