They are no longer replaced routinely with the cap, rotor and plugs. According to experts, changing filters on a regular basis may have more to do with your car's longevity than any other single factor. Oil filters are easy to replace and help prevent unnecessary engine wear. The job of the oil filter is to remove soot, rust particles and other solid contaminants from the oil. Oil filters should be replaced with engine oil every 3,000 miles.
Air filters remove dirt by trapping particles as air passes through the filter media.
They also protect the carburetor in older cars, preventing dirt from clogging the air bleeds and metering jets. They protect fuel injectors in later-model autos. Air filters should be replaced every 20,000 miles but more often if you live or drive in dusty areas. Any filter that looks heavily loaded should be replaced regardless of the number of miles, as should any filter which shows any type of damage. The PCV breather filter assures only clean, filtered air is drawn in through the PCV breather.