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When Should I Change My Engine’s Filters?

Posted by Cummins Expert on

Cummins Fleetguard air, lube, fuel and hydraulic filters help you avoid costly repairs. 

Keeping your engine happily humming means regularly changing out those hard-working filters that protect against wear on critical engine components. But knowing when it's the right time to change your filters is key for ensuring you get optimum service life without sacrificing filter performance. Here's a look at common filter types and when you should consider changing them. 

Air Filters

The right time to change your air filter greatly depends on the frequency and conditions in which you typically drive. Dusty, unpaved roads will clog up an air filter faster than normal highway driving where there is less airborne debris. OEM recommendations for changing the air filter vary greatly, ranging from every 16,000 to 24,000 kilometers, even to 48,000 kilometers in some cases. Again, this service interval depends on where and how often you drive and may not be the same number every time. 

How do you know when it's time to change a dirty air intake filter? Contrary to common belief, visual inspection is not a good indication for knowing when to replace an engine's air filter. Air filters actually become more efficient at removing dust over time, right up until the point of terminal restriction wherein the filter has become too plugged to allow the engine the amount of airflow required for normal operation. Driving around with a plugged air filter can cause the engine to work harder, leading to decreased engine performance and fuel economy. So, a filter that looks dirty upon visual inspection may in fact have plenty of life remaining before needing to be changed. 

The best way of knowing when it's the appropriate time to change an air filter is by using an air restriction indicator. This device measures the level of flow restriction across the air filter, which provides a good indication of the remaining life of the filter. Whenever it is time to change the filter element, however, it's always best practice to inspect the air intake housing to ensure that there are no broken clips, cracks or gaps where dust could bypass the filter. This will help ensure that the system is functioning properly and there are no other related air intake problems that can cause damage to your engine. Remember—as little as one gram of dust is enough to cause engine failure.

Fuel Filters

Unlike air filters, fuel filters become increasingly restricted as they carry out their job of removing contamination from diesel fuel. Where operating environment is typically the limiting factor for air filters, fuel cleanliness is the limiting factor for fuel filters. In other words, the dirtier the fuel source, the quicker the fuel filter will plug. There are three main categories when talking about types of diesel fuel contaminant. The first type is classified as organic contaminants. These particles are usually residual by-products of the fuel refining process and are formed over time due to temperature changes and water in the fuel tank; as this occurs, a thick, black substance forms and will quickly plug fuel filters. These are called asphaltenes. On the other end of the spectrum, cold temperatures can also cause the formation of fuel gelling and paraffin wax. These conditions can lead to blockage of screens, hoses and especially filters.

The next type of fuel contamination is considered inorganic. These particles typically appear as dirt, sediment, wear metals, and other materials not natural to the fuel itself. While these sometimes result from fuel-system components wearing over time, most are introduced to the system through transport and storage of fuel, which are prime chances for debris and particles to fall in. When the storage tank lids are opened to be refilled by fuel suppliers in dirty or dusty environments, the tanks can act as vacuums and suck in all types of unwanted debris. Inorganic particles will lead to shortened filter life when captured, and for particles that are not captured by the filter, these tend to cause premature wear within the fuel system and can lead to the failure of costly high-pressure common rail fuel injection components. 

Last but not least, the third type of fuel contaminant is water. Water is actually the most common form of contamination in diesel fuel, and it is also introduced to fuel through the transfer and storage process. With temperature changes and exposure to the atmosphere, condensation forms inside whatever container is holding the fuel, be it a vehicle fuel tank or a bulk storage tank. The presence of water in fuel is a major obstacle because of the variety of affects in can have on fuel injection equipment, and filtration for that matter. Water in diesel fuel has the potential to lead to problems including corrosion of storage tanks and components, increased wear of fuel-system components due to reduced fuel lubricity, prematurely plugged fuel filters and system components caused by ice crystals which form during cold weather, and even the growth of microbial "slime" that can clog filters, especially in fuel stored over longer periods of time. Once again, vehicle and equipment OEMs will have different recommendations for service intervals for fuel filters, but fuel quality levels will have an impact on the overall service interval for your fuel filters. If you are experiencing the sludge or slime conditions caused by either asphaltenes or micro-bacterial growth, you will need to consider treating your fuel tank and/or fuel supply with a reputable diesel fuel additive, such as one of the Cummins® endorsed solutions offered by PowerService®. 

Oil Filter

Finally, let's talk about oil/lube filters. As stated previously, filter change service intervals will vary by manufacturer and engine application.  Generally speaking, however, the engine's oil filter should be replaced at every oil drain interval. For many of today's newer class 8 trucks in North America, that number is continuing to climb higher than ever before thanks to improving oil compositions and additive technology. However, how you drive can affect whether the oil, and subsequently the filter, needs changing more often. For example, if you primarily drive in stop-and-go traffic or frequently pull heavy loads over shorter distances, this would likely be considered a severe-duty cycle meaning your oil and oil filter may need changing sooner than it would under a normal or light-duty cycle where the engine is under less duress in operation. For example, trucks using the Cummins X15 engine are capable of 96,000-kilometer service intervals under light-duty cycles, whereas that number drops to 40,000 under severe-duty cycle conditions. Regardless of what conditions you normally experience, sticking to a consistent oil drain and filter replacement maintenance schedule will be key to avoiding serious engine wear over time. If possible, it's always a good practice to cut open used oil filters to check the pleated media for any captured metals that would indicate premature wear is occurring inside the engine. Furthermore, oil analysis can be performed by utilizing the Cummins Filtration Monitor® fluid analysis program, wherein you can send oil samples to a third-party laboratory to get a more comprehensive look at how the oil is performing inside your engine.

Cummins Filtration carries a wide range of Fleetguard filters for most common diesel engine types, all of which are backed by the most comprehensive warranty in the industry. Check out our selection of air, lube, fuel and hydraulic filters here.


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