FILTER FALLACIES 10 Misconceptions About Automotive Filters

Although much is made of the high cost of car maintenance and repair, rarely do people think about paying attention to low-cost items that could, if neglected, bring high cost consequences. Take for example the oil filter or engine air filter. These are often undervalued as a maintenance item because more misconceptions exist about them than any other part on a vehicle.  Some of these fallacies are listed below.

Your car’s oil filter sifts out dirt particles the way a filter sifts the coffee grinds in a coffee maker. False. It’s a popular misconception that dirt particles in an automotive filter are strained out no differently than through a filter in a coffee maker. That is not the way an oil filter works. The design of the media in an automotive oil filter forms a kind of maze through which the fluid must ‘negotiate’ its way. With careful engineering, a filter manufacturer such as Purolator, designs the media as a sort of labyrinth through which the fluid will pass but the particles will not.

The engine air filter does not have to be changed nearly as often as an oil filter. False. Most vehicle owners have heard about the necessity of changing the oil and filter at regular intervals but few understand the value of changing their car’s engine air filter. A vehicle ingests 10,000 gallons of air for every gallon of fuel it consumes. In other words, the volume of air that enters the engine is ten thousand times the volume of gasoline. Imagine, if the air entering the engine is dirty – and air along roads and highways contains all kinds of contaminants such as soot, dust and dirt – what will it take for this unfiltered air to damage critical engine components and possibly cause cylinder wear? While you may not notice the effects immediately, over time the presence of contaminants will cause a much greater chance of needing major repairs or a new engine. It is, therefore, just as critical to change the engine’s air filter at least as often as the vehicle’s manufacturer recommends. However, if you drive in particularly dusty or off-road conditions, it’s a good idea to change the air filter more frequently.

Changing the air filter does not impact the cleanliness of the oil and the engine. False. If a car’s engine air filter has been neglected, it will allow dirt to enter the engine and make its way past pistons and piston rings and into the oil supply. This can potentially destroy key internal components. More important, once the damage sets in, there is no turning back. By now, dirt that has entered your engine may well have damaged the valves and valve seats, the piston rings and cylinder walls, and the engine bearings. This may ultimately mean replacing your entire engine at a cost of $4,000 or more, plus all the aggravation that will go along with the experience.

Always follow the ‘normal’ service schedule in your owner’s manual when changing your oil filter. False. The fact is most of us, most of the time, drive short distances, which really calls for us to follow a ‘severe,’ not ‘normal’ service schedule. The reason is that if your vehicle is not driven on the highway for long distances, the oil does not have a chance to get hot enough for water condensation and raw fuel to evaporate out of the crankcase. Over time, this condensation builds up and can lead to costly damage to internal engine parts.

All filter media are the same. False. “There’s a great deal of science that goes into the development and manufacturing of filtering media, and the media used in oil filters is not at all suitable for engine air filters or fuel filters. Each type of filter requires a unique media in order to function properly,” explained Kevin O'Dowd, Director of Marketing & Communications for MANN+HUMMEL Purolator Filters.

With oil filters for example, “the filtering media must be fine enough to capture and hold even the tiny particles that can cause engine damage without restricting the free flow of oil to critical internal engine components, ” said O'Dowd. “Our decades of experience allow us to strike the perfect balance of maximum filtration with minimum restriction. So, for instance, the media in our Purolator PureOne premium oil filter is able to capture 99.9 percent of particles that are smaller than a thousandth of an inch. And our Purolator Classic oil filter can capture 97.5 percent of those same tiny particles. This ability to capture particles is known in the industry as ‘efficiency,’” O'Dowd said.

The capacity of the filtering media (i.e. the ability to hold particles) is equally important, continued O'Dowd, “so motorists should insist on a filter with the greatest capacity to hold particulates without compromising filtration.”

Nothing can be done about the unpleasant odors on the road, for example, in a construction area or in farm country. False. Many motorists don’t know that if their vehicle is a 2001 model or newer, it is probably equipped with a cabin air filter, a device that is designed to keep the air in the interior of the car clean and free of dust, smoke, and even unpleasant odors that enter through the vents even when the windows are rolled up.

Two kinds of cabin filters are available for modern vehicles – the particulate cabin filter and the activated charcoal cabin filter. Purolator for example, offers BreatheEasy cabin air filters that feature specially engineered media to capture and hold even the finest particles of environmental contaminants such as dust, soot, pollen, fungus and bacteria. These filters are electrostatically charged, similar to many household HVAC filters, to ensure that particles stay attached to the filter.

In addition to the particulate filter mentioned above, Purolator also offers the activated charcoal cabin filter that adds the capability to keep odors out of the car’s cabin. The activated charcoal cabin filter adsorbs (captures and holds) most toxic and foul-smelling gases such as ozone, nitrogen oxide, sulfur dioxide and hydrocarbons. Either type of cabin air filter may be available depending on the make/model of your vehicle. To see if a vehicle has a cabin air filter, refer to the vehicle owner’s manual or visit the Application Guide on Purolator’s website at

It’s a waste of money to change your filters too often. False. There is practically no one that changes their vehicle’s filters too often. If anything, they don’t change it often enough! Take for example, the engine air filter. Just as breathing clean air contributes to a long and healthy life, so also a vehicle’s engine that ‘breathes’ clean air performs better over a longer period of time. Abrasive dust, dirt and other contaminants that can enter through the engine’s air intake ducts while driving can damage a car’s internal engine components, increase wear and ultimately reduce the engine’s power, performance and long life.

All filters are pretty much the same. False. Filtration is all about capturing and holding debris and contaminants that could otherwise cause gradual wear or even catastrophic failure of your engine. “The quality of a filter really depends on the technology behind it,” said O'Dowd. And, since most oil filter features are buried deep inside the filter, it’s easy to assume that all oil filters are the same. But they’re not,” he said.

“Even the basic materials in an oil filter can vary widely,“ said O'Dowd. Some filters use thin steel for the case, which can burst under pressure spikes. And some filter manufacturers even cut corners by making internal end caps out of cardboard rather than metal. Since most oil filters features are hidden inside, you have to rely on the integrity and reputation of the manufacturer to supply a filter with high quality components.”

When it comes to filters, the brand name does not matter. False. Reliability comes with respected brands. It is a good idea to rely on manufacturers who stake their decades of reputation on the design, construction, and performance of components, materials, and engineering that, for the most part, go unseen once they’re assembled. So motorists and do-it-yourselfers (DIYers) should trust engines to filters made by those who have pioneered innovations like Purolator that invented the very first automotive oil filter, the first full-flow oil filter, and the spin-on oil filter.

Changing a cabin air filter is a difficult and time-consuming process and there’s no one to turn to for assistance. False. Replacing a vehicle’s cabin air filter is easy in many cases. Usually found under the dash, behind the glove box, or in the air box in the engine compartment, cabin air filters can normally be installed in anywhere from less than 10 minutes to about an hour, depending on the location. Most Purolator BreatheEasy cabin air filters come with an illustrated, vehicle-specific instruction sheet to assist with installation.

Not only that, available to everyone – service professionals, DIYers and the motoring public – are the Purolator PROs (Purolator Response Office), a team of experts who will answer any filter-related question, free of charge, via personal e-mail within 48 hours. Purolator PROs can answer virtually any question about filtration – from application data, dimensional specifications, media design and configuration to installation procedures. Purolator PROs can be contacted through the company website at Or, you can call the toll-free Purolator hotline at 1-800-526-4250 between 7 a.m. and 6 p.m. CST Monday through Friday and on Saturdays from 8 a.m. until 4 p.m. CST.

Refer to the owner’s manual to see if your vehicle has a cabin air filter or visit the Application Guide on website to find a vehicle’s BreatheEasy cabin filter.

For best results, Purolator recommends changing your vehicle’s cabin air filter every 12,000 to 18,000 miles or per the vehicle’s manufacturer’s suggested intervals in the owner’s manual.

Purolator PureONE Oil Filter Cutaway
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