Filters – Their Evolution
Filters are found in the engine air intake, passenger air intake, engine oiling system, automatic transmission, fuel system and the EVAP system, and they are divided into two categories: air and liquid filters.
Air filters
Originally, the engine air filters consisted of an oil bath and filter media capable of holding a large amount of dirt, but were messy and awkward to service. They have been replaced with the media mesh filters that we are familiar with today, which can be made of paper, foam and cotton.
Modern air filters are rated based on the amount of air born particles they capture. These ratings are typically a letter and number designation such as G1, G2 and so on.
Filter categories
Where applicable, the primary and secondary filters range from G1 to F9. The ones used on vehicles are in the F5 to F9 range. The cabin filters, which remove dust and pollen from the air, are rated above F9.
Service intervals on engine air filters were typically tied to the vehicle oil change interval, but as manufacturers increased the oil change intervals, air filters had to last longer as well.
Oil filters
Long life oil filters have a pore size of 3 to 5 microns and have successfully increased the oil change interval to 15,000 kms while providing the required protection for the engine.
Transmission filters
Some fluid filters such as oil and transmission filters have extended service intervals, although many transmission filters do not have any, so they have to provide protection for the life of the vehicle. The transmission pressures are monitored by the ECU, and a low transmission pressure code could be caused by a dirty filter.
EVAP and cabin filters
Other air filters, such as the EVAP filter, have no service interval and are serviced as part of the EVAP canister assembly or are serviced only when they present a problem and the Check Engine Light turns on or an EVAP code is set.
Cabin filters, such as the Affinia with Bioshield 75 technology, eliminates air born microbes and pollen. These type of filters are the fastest growing segment in the filter market.
