An air cleaner is used to keep airborne dirt and dust out of the air flowing through the engine. This material, if allowed to enter the engine, would form an abrasive compound in conjunction with the engine oil and drastically shorten engine life. For this reason, you should never run the engine without the air cleaner in place except for a very brief period if required for trouble diagnosis. You should also be sure to use the proper replacement part to avoid poor fit and consequent air leakage.
Proper maintenance is important since a clogged air filter will allow an ever decreasing amount of air to enter the engine and, therefore, will increasingly enrichen the fuel/air mixture, causing poor fuel economy, a drastic increase in emissions and even serious damage to the catalytic converter system. The maximum maintenance interval on all models is 30,000 miles (48,000 km). Maximum efficiency is maintained by changing the filter more often. Diesel engines are particularly sensitive to partly clogged air filters and will lose performance if not well maintained. In all cases the air cleaner element must be replaced; it cannot be cleaned.