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Making the informed choice: Filter Quality

By autotech-nath on October 9, 2019

As the difference between a decent and sub-standard replaceable filter is not immediately obvious, Rob Marshall enquires with both OE and Non-OE suppliers about how technicians can select quality parts with confidence.

Due to motorcars becoming more complicated, more precise and boasting lengthy service intervals, effective, consistent and long-lasting filtration has become ever-more critical. Low grade products might look as if they will do the job on first glance but, as engine damage especially builds over a period of time, the consequence of using poor quality filtration might not be associated with a sudden and expensive mechanical failure. 

Using low grade filters also presents a warranty risk, when maintaining a vehicle that is still covered by the manufacturer, or supplying main dealer. While you are not duty-bound to buy filters from a franchised parts counter, the customer will have to demonstrate that he/she has used OE quality filters and itemising the brand and part number on the invoice should be part of the customer service remit. 


First Line told AT that the filtration market overall is very sensitive to prices, which are being driven-down continually. As some manufacturers are cutting quality to meet a particular cost base, First Line advises that garages should protect themselves and their customers, by sticking with reputable, established brands that manage and control the specifications of their products carefully, as it does with its Borg and Beck brand of filters. 

Issues can occur at factor level. MAHLE reports that, when garages request that a service kit is delivered, parts can be supplied that originate from several different manufacturers. This should not be a problem, provided that those makes can be trusted, but MAHLE advises that quality brands are specified by garages to their parts suppliers, in order to protect their reputations. 

On modern canister filter designs, only the filter medium is replaced; the anti-drain back and bypass valves are incorporated within the filter module.

UFI Filters Group concurs that, while filters look very similar on the outside, performance levels deviate enormously. Buying and fitting a cheap aftermarket filter might seem to be a good way of cutting costs and, potentially, boosting profits but it can be a false economy for you and/or your customer. UFI says that they can cause damaging particles to remain within the engine, due to either an oil filter failing to separate them from the oil, or that they have entered the engine via the air, or fuel filter. This compromises not only engine performance and reliability but also increases fuel consumption and harmful exhaust emissions. 


Out of all filters discussed, the spin-on oil filter is the most mysterious type, because all of its working parts are enclosed within the metal canister. Apart from the filtration medium itself, a flap valve (although some filters are equipped with two) is fitted that stops the oil from draining from the filter, after the engine is switched-off, to prevent oil starvation on start-up. A calibrated bypass valve also features, to ensure that the oil flow avoids the filter, should it become blocked. 

UFI told AT that, presuming that these required technologies are installed in the first place, it has encountered bypass valves on low quality filters that open at higher (or lower) pressures than specified, increasing the risk of unfiltered oil passing through the engine, thus raising engine wear levels. By comparing budget filter quality against its own standards, MAHLE has discovered poor machining, resulting in sharp metal burrs that could detach from the filter, as well as anti- drain back valves that are either misshapen, and/or made from thin rubber, which reduces their effectiveness, plus a lack of glue that holds the relevant components together. 

The cartridge-type oil filter is far simpler and easier to inspect, because its filtration elements are exposed and the bypass and anti-drain functions are performed by the assembly, into which the filter locates (referred to by UFI, for example, as the filter module). As with spin-on filters, low quality cartridge filters can suffer from manufacturing inadequacies. MAHLE reports of poorly folded filter materials, while UFI highlights that the performance of the filter material (also called ‘media’) may be generic and unmatched to the specific engine application, which can result in either particles entering the lubrication circuit, or the filter clogging prematurely. The company explains that developing the filtration media is a complex science; neither must it degrade on contact with acids, soot and bio-fuels, nor affect oil pressure, while filtering contaminations effectively. Even the cartridge dimensions play an important role in determining optimum filtering efficiency, while minimising the risk of clogging. UFI explains also that modern engine technology has seen a shift from a cellulosic oil filter media and the latest engines, especially turbocharged units, have filters that are specified with glass-fibre, or polymer materials. As with engine oil, therefore, downgrading oil filter specifications is not a wise idea. 


While it is obvious that an air filter affects the air quality that is delivered into the combustion chambers, it is not always appreciated that the filter controls air flow stability, too. Therefore, to ensure optimum performance, while mitigating wear and harmful exhaust emissions, air filter specifications are factored by the carmaker and replacement parts must match them. 

A sign of a good quality air filter is it possessing a pre-filter that removes larger particles, such as road dust. This extra fleece layer can increase filter capacity by up to 40%.

When working with a vehicle manufacturer, when a car model is being developed, MAHLE explains that the location and filter replacement interval defines the most apposite filtration material and the physical dimensions to achieve the required filtration and flow rates. The company also explains that maintaining a constant air pressure is critical, because these values are monitored continually by the engine management system. In addition, MAHLE highlights that specifying the pressure differences between a turbocharger’s intake and exhaust turbines is a precise science and any subsequent modifications (such as installing a poor-grade air filter) that reduces the pressure within the air intake can damage the turbocharger over a period of time. 

Yet, you may encounter performance upgrade air filters that have been fitted to a customer’s vehicle at some point in the past. Obviously, some of these types may not require replacement but might need maintenance, such as cleaning, or oiling, to maintain their filtration properties. AT asked both MAHLE and UFI about these types of filters generally, with no reference to any brand. The advice that we received was that, while such filters could increase airflow, it would be at the expense of filtration effectiveness. Furthermore, airflow meters are calibrated to work with an OE specification filter, so any deviations can, perversely, result in a drop in engine power. The use of ‘more open’ engine air filters and the resultant imbalance that is created can also cause increases in fuel consumption and exhaust emissions, while risking an increase in oil contamination rates and accelerated wear levels on internal mechanical parts. This may be why certain makers of ‘racing’ air filters state that the ECU should be ‘calibrated’ after the element is installed. 


Again, fuel filters have changed from the washable gauze-type that was fitted to many carburettor engines (although it is easy to forget that a strainer mesh is still fitted to the in-tank lift pump on many modern cars) to the canister-type, fitted to the underside of the vehicle on many petrol engined cars. Cartridge-type fuel filters (as pictured) are now commonplace, although their initial prevalence on diesel engines was because of the issues associated with the fuel, including water contamination and microbe-related infestation.

As pressures and tolerances have risen on both diesel and petrol fuel injection systems, so too has the sensitivity to fuel contamination. MAHLE reveals that even the smallest particle can cause premature wear and require costly replacement of both the high-pressure pump and injectors. Water in the injection system can cause a loss of performance, injector damage and even component failure. In some applications, water separation is a core function of the diesel filter, as specified by the vehicle manufacturer. UFI highlights its new Gen2Plus filters, which it claims sets new standards in the separation of water residue from the fuel and its ability to filter impurities from the fuel; the first application of which was in the current-production Fiat Tipo. 


While the informed technician knows why it is beneficial to install OE quality filters to protect the engine and its ancillary components, a typical customer may not be as technically- minded, which is why the garage has to make the decision for them. Perhaps, therefore, the only opportunity you have to upsell filtration products to the customer lies when the cabin filter is due for its annual replacement, because it has direct implications for the occupant’s health and comfort, which are easy to explain and understand. 

First Line has produced a poster to inform customers about the importance of changing cabin filters and the potential upgrade options. To request a free poster for your customer waiting areas,

First Line says that educating the end user about the importance of changing a cabin filter annually is a major challenge for the filtration industry. Comline agrees and argues that opportunities are not being grasped by many garages. “The cabin filter is a relatively low-cost item, which offers motor factors and garages fantastic growth opportunities,” advises Nick Weir, Head of Comline’s Business Line Operations, who continues: “The key lies with consistent education and we urge motor factors and garages to join us, as we strive to highlight the benefits of a fully-functioning cabin filter. With NHS figures reporting that a fifth of the population now suffers from hay-fever, there has never been a better time to convey the cabin filter message.” 

Mr Weir also reports that the carbon-activated cabin filter offers an ideal upselling opportunity, because it provides additional protection against ultra-fine gases, such as particulates, benzine and ozone, while absorbing unpleasant odours, which may otherwise enter the cabin. These may be worth emphasising, should you have a customer that drives frequently in urban conditions, for example.  

Many other filter manufacturers offer upgraded cabin filters, too. MAHLE offers its Caremetix range; MANN has its Frecious- Plus and UFI announces that its anti-bacterial ARGENTIUM range will be launched next year. AT will keep you informed of further developments. 


Deciding on which filters to fit to your customers’ cars is a balance between your brand preferences, its range, what your factor supplies and the speed of delivery. From a quality perspective, OE manufacturers that design filtration solutions for car companies and supply their main dealers with replacement parts emphasise their OE quality credentials that are closely monitored and controlled. Such companies also take action against any counterfeiters, although such cases are rare in the UK. 

Do not discount non-OE suppliers, either, provided that they can demonstrate that their filters are of OE quality, at the very least. First Line told us that, prior to cataloguing a new product, it goes through extensive quality control processes and, although First Line admits that it is not a manufacturer, it uses the, “very best manufacturing partners, all of which are subjected to regular quality audits in line with First Line’s ISO:9001:2015 procedures.” 

The company also emphasises Borg and Beck’s 100 years of heritage and states that all of its filters are warranted throughout the relevant vehicle’s service interval. Like First Line, Comline engages some of the largest and most respected production facilities in the world, which comply with latest ISO standards. Aside from monitoring its suppliers directly, it also tests filters in its own laboratory, including performance and ease of fitment assessments. Comline also partners with the International Filter Testing Service (IFTS). 

The company told AT that IFTS membership tends to be the preserve of an OE filter manufacturer; the organisation also conducts impartial tests that underpins Comline’s confidence in its filter range’s quality. To assist technicians further, Comline reports that its entire range is backed by a comprehensive data portfolio, which includes product specification, application data and fitment information, all of which is available via MAM, Autocat and TechAlliance. 









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