The air flowing under a vehicle’s hood is full of contaminants – everything from airborne vegetable matter, dust, dirt, and insects to moisture and exhaust soot.
The air filter allows the engine to get the air it needs with little resistance, while at the same time making sure the air is as clean as possible.
An automobile engine is really an air pump. When more air enters the engine it increases the efficiency of the combustion process, thereby increasing both horsepower and torque.
Airflow becomes a problem when it passes through a filtering medium. The amount of resistance to the airflow depends on the physical attributes of the filtering medium.
Air filter manufacturers K&N explain the importance of airflow to racing engines: “The performance benefits of maximum airflow are clear, compelling and well documented.
“That is why so many professional racers are willing to run expensive vehicles with no air filter, as opposed to installing a disposable air filter. They are seeking the additional horsepower and throttle response needed to win the race.” (knfilters.com, Facts You Should Know About Air Filters)
Air Filters Prolong Engine Life
When it comes to passenger vehicles, air filters improve engine efficiency and prolong the life of the engine, whether gasoline-powered or diesel.
Today’s air filters are effective and easy to maintain. They are constructed of fine mesh screens, pleated paper, and an outer screen.
How often air filters should be replaced depends on a number of factors. A filter that lasts 20,000 or 30,000 miles on a vehicle that’s driven mostly on freeways may last only a month or two in harsh conditions where the vehicle is driven frequently on dirt and gravel roads.
Andrew Bernhardt, an auto enthusiast, and writer for the AutoAnything website suggests: “Perform a visual inspection of your air filter every 10,000 to 12,500 miles. If it still looks OK, pop it back in and check it when you hit 20,000 to 30,000 miles of use.”
When an air filter needs replacing, do it without delay. It’s truly one of those car repairs you can’t afford to avoid.
Consider the Air Filter’s Environment
Before deciding on the time limit for keeping a filter in service, consider the conditions in which it operates. Despite air pollution, the city is a lot friendlier environment for filters than most rural areas.
Regardless of the distance traveled or time in service, air filters should be replaced before they begin to cause a significant restriction to airflow. Once this happens, fuel economy, performance, and emissions start to deteriorate.
To see how dirty the filter is, simply remove the filter and hold it up to a 100 watt light. The darker the filter, the heavier the load of dirt it has embedded in its elements.
Don’t bother to try cleaning the filter. It’s a difficult task, to begin with, and would take more time than it’s worth even if it could be done. Once dirt particles are embedded in the filter they’re almost impossible to dislodge.
All Air Filters aren’t The Same
The air filters in modern cars aren’t all of the same construction. The 100 Watt light bulb test works with pleated paper filters, but as the Automotive Car Driving Dealer website tells us, this doesn’t work on all vehicles.
“Some cars have extended-life factory filters with dense filtering media that are highly effective but do not allow light to shine through. Replace these filters at the mileage interval specified by the manufacturer.’ (ashfire.net, Are You Replacing Your Air Filter Too Often?)
So, if in doubt, always refer to the vehicle’s owner’s manual for guidance. Air filter replacement is usually stipulated at specified intervals, but these should be seen as the maximum length of a filter’s service life.
More frequent changes won’t cost much and they’ll ensure dirt isn’t being forced into the engine.
If the vehicle does a lot of traveling in dusty, dirty conditions ask an automotive technician to check the air filter at every service interval.
As a general rule, if a filter looks really dirty when a light is shined on it, replace it. Air filters are not expensive, but they are an essential component of every motor vehicle.