An air filter is made from paper or other media to trap dirt and other foreign particles as dirty air passes through the filter. There are tiny holes in the media that allow the air to pass through and these holes stop most particles.
Air filters are not 100 percent efficient at trapping dirt particles. Most new air filters are 97-99.9 percent efficient. A small amount of dust or dirt can pass into the engine. As the air filter builds a dust film, the holes in the media become smaller, and the filter becomes more efficient at trapping dirt.
As the filter traps dirt, it is more difficult for the air to pass through the filter, and restriction increases in the air induction system.
The Filter Minder® measures restriction or vacuum. The air filter service indicator is calibrated per engine or vehicle manufacturer's recommendations.
The air filter should be serviced when the position indicator of the service indicator approaches or reaches the red zone.
Use of the Filter Minder® helps maximize filter service life, prevents excess fuel usage from overly restricted filters, and saves on operational costs.