An Engine Air Filter: How Much Dirty Air Does It Handle?

How much dirt and debris can a car’s engine air filter keep out? Depends on whom you ask. The average motorist will probably not know. But ask Kevin O'Dowd, and you can expect to hear, “Much more than you would expect.” And O'Dowd would know. He is an executive for MANN+HUMMEL Purolator Filters, a company with a long-standing history in the field of filtration. After nearly 90 years in the business, Purolator is still one of the largest suppliers of high quality automotive filters to the North American Aftermarket.

Most of us who drive know that a car runs on a combination of gasoline and air. Picture this: for every gallon of fuel/gasoline that your car consumes, it also consumes about 10,000 gallons of air, which is almost the same amount of air as is contained in a 12X24-foot swimming pool with a depth of 5 feet ( Now imagine that with every gallon of fuel, a swimming pool worth of dirty air is also entering your vehicle!

“Roadside air contains all manner of contaminants such as soot, dirt, leaves, straw, and tiny bits of rubber. Without proper filtration this dirty air can potentially damage a car’s internal engine components, increase cylinder wear, and ultimately reduce the engine’s power,” said O'Dowd.

When selecting an engine air filter, O'Dowd advises that one should be mindful of two important criteria – the filter’s 'capacity' and 'efficiency' in capturing the dirt before it enters the engine combustion chamber. 

“Capacity is the amount of dirt the filter can hold before it begins to restrict air flow and efficiency describes how well it does its job,” O'Dowd said. Modern engines that are built to be more fuel-efficient and have smaller orifices and tighter tolerances call for engine air filters that can trap even the smallest particles of dirt threatening to enter the system.

For instance, Purolator’s PureONE air filter’s, high-capacity media offers up to twice the capacity of conventional filters1 to trap contaminants smaller than the size of a grain of sand and is 99.5 percent efficient in capturing particles 20 microns or larger (one micron is one millionth of a meter). This means it traps 99.5 percent of particles that size or larger. Likewise, Purolator Classic air filter’s high-density media traps 96.5 percent of contaminants.

Equally important is the design and construction of an air filter because it determines how well it will supply an engine’s need for clean air. Today’s sophisticated fuel-injected engines normally use a flat, rectangular, panel-type air filter featuring a specially formulated paper or cellulose media that removes particulates while maintaining minimum resistance to air flow.

Air filters that claim to remove really small particles may have too much resistance to air flow. Other suppliers may claim to sell filters with very little resistance to air flow but actually achieve that by opening up the pores and allowing bigger particles to enter the engine. Either alternative may harm your car’s engine.

“The goal is to use a filter that strikes the best balance between capturing contaminants and not restricting airflow,” said O'Dowd. “Our Purolator PureONE and Classic air filter are all engineered to achieve that precise balance.”

O'Dowd explained that the media in a panel-type filter is attached to a binding so it can retain its shape. If the adhesive used to attach the media to the binding framework is of inferior quality, it may melt or soften due to high under-hood temperatures. This may cause the media to pull away leaving a gap and allowing unfiltered air to enter the engine and do damage. Or, if the air filter begins to get clogged, the engine vacuum can suck in the media, once again allowing unfiltered air to bypass and enter the engine compartment.

Purolator recommends that most people change their vehicle’s engine air filter once a year or every 12,000 miles, unless the car is being driven in unusually dirty or dusty conditions. Because of the long intervals between changes, it’s important to install the best filter possible for reliable and efficient filtering.

“The good news is,” O'Dowd said, “changing your car’s air filter is quick, easy and inexpensive.”  Older cars often had a radial air filter resting in a round housing under a lid held in place by a wing nut. Today’s more advanced fuel-injected engines normally use a flat, rectangular panel-type air filter that resides in black plastic duct work in the engine compartment. Usually, all one needs to do is release several clamps, separate the housing halves, lift out the old filter, and install the new one. “It’s usually that simple,” O'Dowd said.

“Imagine,” O'Dowd said, “with a swimming pool worth of dirty air coming at your engine with every gallon of fuel you use, the question remains, is your engine air filter up to the task?”

1 Based on ISO 5011 on PA 24278) 

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A Clean Engine Air Filter
A Dirty Engine Air Filter
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