All engines are equipped with dry type air cleaners that utilize replaceable air filter elements. The Positive Crankcase Ventilation (PCV) system air filter element on gasoline engines is also found in the air filter housing (usually mounted on the inside of the housing rim). Both of these filter elements should be replaced at 30,000 mile or 1 1 / 2 year intervals (36 month intervals on 1983 and later models) on all models, except in extremely dusty or smoggy conditions where replacement should be much more frequent.
Never remove the air cleaner from a diesel with the engine running. The intake vacuum is strong, and dirt or nearby objects (even the air cleaner wing nut!) may be sucked directly into the combustion chambers. This will almost always cause major engine damage.