Function of an Oil Filter
The function of an oil filter is to remove contaminants from your engine oil to prevent them from continuing to circulate within your engine. Whether you use conventional or synthetic oil, contaminants that circulate through your engine via your oil can damage a variety of parts. In fact, any contact surface in your engine will wear more quickly with contaminated oil including but not limited bearing surfaces (rod bearings, main bearings), camshaft lobes, piston rings, etc.
In order to remove debris from your oil, the oil filter is placed inline such that your oil must flow through it as your oil pump circulates oil throughout your engine. The filter typically contains a paper element that allows oil to pass through while trapping any other debris. Debris accumulates until you eventually change your oil filter out for a fresh one, so it’s important to stay up to date on your oil filter maintenance.
Common Symptoms of a Bad Oil Filter
Fortunately, there are very few ways that an oil filter can fail. As such, they tend to be a pretty reliable part and replacement tends to occur as part of routine maintenance rather than to fix a faulty oil filter. As such, when it comes to oil filters, prevention is the key as most failures tend to occur in oil filters that have surpassed their recommend service interval. That said, oil filters can still fail and their potential failures are divided up into three categories:
Leaks
Sometimes the seal or filter housing itself can become compromised, in which case it starts to leak. Depending on the size of the leak, this can be a relatively minor issue or something that needs to be addressed immediately. Leaks are rare and are usually due to improper installation or physical damage to the filter caused by external factors such as an errant mechanic or fender bender.
Clogs
If left unchanged for extended periods of time, oil filters can accumulate enough debris to become clogged. The result is that oil has difficulty flowing through them. This can impede oil flow throughout the engine, which can result in oil starvation as oil no longer freely flows through the filter. This can quickly lead to engine failure if left unattended, however this will often trigger an oil pressure light on your dashboard.
Torn/Damaged Filter Element
This can be a tough one to spot, as it won’t have any outward symptoms. Essentially, a torn filter element within your oil filter means that oil can freely pass through your filter without actually being filtered. In other words, oil flow isn’t disrupted but the filter stops working. If this persists long enough, your engine may experience excess wear or failure, but depending on time frame you may also not notice at all. Fortunately, routine filter changes when you do your oil changes limit the damage that this can cause.
Replacing an Oil Filter
An oil filter is typically done as part of an oil change, and as such, we have listed some typical steps to complete an oil change below.
Note: The example steps below are intended for general informational purposes solely to help give you an idea of project difficulty and tools required. As all cars are engineered differently, repair procedures and safety hazards vary from vehicle to vehicle. To ensure that you have a vehicle specific repair procedure and an exhaustive list of potential safety hazards, we advise you reference a factory service manual for your vehicle. Similarly, referencing a repair manual such as Chilton or Haynes might serve as a less expensive alternative.
Step 1 – Make sure your oil is cool enough to work on your engine.
Step 2 – Depending on the height of your vehicle and location of your filter, you may or may not need to lift your vehicle off the ground. You can do this by either using a high quality floor jack or by driving your car up on a set of ramps. If you use a floor jack, make sure to support the vehicle with a set of jack stands.
Step 3 – Drain the oil. You can usually locate this visually, but if not, your owner’s manual can identify the location of the drain plug on your oil pan. A socket wrench can be used to remove the drain plug. Before removing the drain plug, double check that your engine is cool to avoid potential burns from oil that is too hot. You can oil remove the oil filling cap on top of the engine to avoid oil sloshing as it drains. You should collect the oil in an oil drain pan to make for easy disposal and cleanup. If you feel so inclined, this is a good time to collect some oil for oil analysis if you want to measure the internal health of your engine.
Step 4 – Remove the filter. For screw type filters, use an oil filter wrench or similar in order to grip the filter and unscrew it. For housing type oil filters, use a large socket to unscrew the filter housing cap and pull the filter out.
Step 5 – Replace the oil drain plug. Once the oil has stopped dripping, you can replace the plug by threading it back into the oil pan. Be sure to not cross-thread the plug and make sure the gasket on the plug is in good condition. You can also change the gasket (or crush washer depending on vehicle) before installing the plug. Tighten the plug until it is finger tight with your hand and then use a socket wrench or a combination wrench to snug the plug up. Don’t over-tighten the plug or you could strip the threads which would require a new oil pan which can be expensive.
Step 6 – Install the new oil filter. Before you install the new oil filter, lightly coat the rubber seal with new oil to ensure you get a good seal and inspect the oil filter for any damage or defects. For screw type filters, screw the new filter onto the engine and turn until the seal makes contact with the housing surface. The filter should be snug to ensure it won’t leak but do not overtighten of you risk damaging the filter. You shouldn’t need to use any tools to install the new oil filter. For housing type filters, just place the filter in the housing, make sure the seal is seated, and screw on the top until snug and tighten using the large socket you used during the removal step.
Step 7 – Add new oil to the engine. Use a clean funnel to pour new oil into the engine to avoid spills. Your owner’s manual will describe the type of oil, correct oil weight, and quantity you need to add for your specific vehicle. When you have added the correct amount of oil, replace the oil cap. You should always confirm that the oil level is correct with the dip stick. More modern cars may have a gauge on the instrument cluster that monitors oil level, but we are old school and always like to confirm with the dip stick anyways if the car has one so that is what we recommend. Replace the coil cap once the oil level is correct.
Step 8 – Start the engine and look for leaks. The most common spots for leaks after an oil change are the drain plug and the filter since these are the components that were removed. Once you have confirmed that there are no leaks, you can turn the engine off and allow the vehicle to sit for a few minutes. The wait period will allow the oil to drain back down into the pan at the bottom of the engine.
Step 9 – Verify that the oil level is good after the car was run. After a few minutes, most if not all of the oil will have drained into the pan. Check the engine oil level and add any additional oil necessary to ensure the oil reads full on the dipstick. Always use a clean towel or rag to wipe the dipstick to avoid getting contaminants in your oil. Use caution as your engine may be hot after running.
Step 10 – Make sure you dispose of the used oil and filter properly. Most auto parts stores and quick lube shops will recycle used oil for free and you may also have a recycling center in your area that take used oil. Improperly disposed oil creates significant negative environmental impact so please be responsible. Once complete, you can put your car back on the ground and go. It is good practice to check your oil level occasionally (we do it every 1000 miles on our cars) and top it off as necessary in between oil change intervals.
Best Oil Filter Brands
Oil filters are one of the most commonly replaced components on your vehicle. Considering how important they are to the lifespan of your vehicle, it pays dividends over the long term to make sure you are using the best! Below are our recommendations for our favorite oil filters that we have used for our vehicles. We hope that this helps narrow your search for the best oil filter.
Mann
Mann is a German company founded in the late 1930s that has been making oil filters for almost its entire existence. As such, they have a ton of experience when it comes to making high quality filters. They provide OEM parts to many of the major vehicle manufacturers, particularly the German vehicle manufacturers such as BMW, Mercedes, VW, and Audi. They continue to develop products with the focus of leading technology in the filtration segment. Overall, we have always had great experiences with all of Mann’s filters ranging from oil filters to air filters to cabin filters due to the high quality. In our experience, you really can’t go wrong with a Mann filter!
Click here to find a Mann oil filter for your vehicle.
Mahle
Like Mann, Mahle is a company that also supplies OEM filtration components to the likes of BMW, Mercedes, Audi, VW, and many others. They also develop components that are used in racing series such as in Formula 1, the technology from which eventually trickles down into their consumer products. They are widespread and produce filters for most vehicles on the market today. They have a high quality to value ratio, meaning that you get great quality parts at a reasonable cost. Mahle makes great filters that have always worked perfectly for us. As such, we give them a strong recommendation.
Click here to find a Mahle oil filter for your vehicle.
Wix
Wix is another brand that just downright makes good filters. They make a variety of components and are readily available pretty much anywhere. The quality is high and the price point is very attractive. Wix also makes filters for most vehicles, unless you have something very specialty or niche. We have never had any quality issues with Wix filters and like the two previously mentioned brands, Wix is one of our go-to choices when doing oil changes. We think you’ll be highly satisfied if you decide to give them a try.