How Oil Filter Functions, Cost, Importance, and Other FAQs


The oil filter function plays a key role when it comes to engine performance and health. Simply put, the oil filter protects the engine. It filters out all the particles from the oil and prevents them from entering the engine and causing damage.

”The oil filter as an essential part of the lubricating system has a function to remove foreign particles from the engine oil in a highly efficient manner and to prevent damage and premature wear to the engine and it’s moving parts.”

How Oil Filter Functions

Is the oil filter necessary? The oil filter is necessary because the main task of the oil filter is to protect the engine by filtering out the foreign particles that can cause damage to the engine. This makes it a key component in engine health and performance. The oil filter function is to separate particles from the oil in a highly efficient manner. The engine oil enters the oil filter through the cover and then goes through the filter medium where all the small particles are trapped and then the oil exits the filter through the cover and goes into the engine.

How Oil Filter Functions

A non-return valve prevents the oil filter from running dry after turning off the engine and ensures engine lubrication right after starting the engine. In the case of viscous oil, e.g. in case of low temperatures, the bypass valve makes sure the engine is constantly supplied with oil bypassing it by the filter for short instants.

The oil filter must be changed regularly. If the oil filter is clogged, the bypass valve stays open and unfiltered oil gets into the engine which increases engine wear.

Parts Of Oil Filter

The oil filter design might seem a bit different for different types of vehicles, but, they all have pretty much the same parts.

  • Gasket: Made from a specially selected material which ensures the filter is tight. Resistant to changing thermal and mechanical loads.
  • Cover: with precisely made high-strength thread. Provides a permanent connection to the motor filter.
  • Anti-Drainback Valve: Protects against a temporary shortage of oil during engine start-up. Specially designed structure made of flexible material.
  • Filter Medium: Made of high-quality materials tailored to each specific model. Resistant to aggressive chemical components of synthetic oils.
  • Evenly Distributed Pleats: Thanks to special ribbing in the filter media. Ensure high absorption of the filter and minimum differences in pressure.
  • By-Pass Valve: Ensures oil supply to the engine even when running the vehicle at low temperatures. The pressure of opening the valve is precisely tailored to each specific model.
  • Pressure Spring: Prevents unwanted movement of the filter cartridge inside the housing. Ensures the tightness of the internal filter elements.
  • External Housing: Powder coated. Resistant to corrosion and mechanical damage.

Types of Oil Filter Operations

The oil filter has 2 types of operations: Standard flow and emergency flow. As the name suggests, the difference between the standard and emergency flow is the time when the operation is activated.

Standard Flow Operation

At standard flow operation, the engine oil enters the oil filter and goes through the filter media where it gets filtered and then leaves the oil filter and goes into the engine. This is called a standard flow operation because this is how the oil filter works in normal circumstances. If the oil filter is clogged, the flow changes from standard to emergency.

Emergency Flow Operation

Emergency oil flow occurs when the filter becomes clogged due to oil not being changed at appropriate intervals or during engine start-up at low temperatures (when the oil is cold and thick). In this case, the oil bypasses the filter media and is taken directly to the bottom of the oil filter where it passes through the bypass valve and leaves the oil filter.

What Does The Oil Filter Attach To?

The oil filter is attached to a pipe or drilled oil passageway known as the oil gallery which in most cases is located on the bottom side of the engine block. The oil travels inside the engine and lubricates it thanks to the oil pump.

Image by: www.machinerylubrication.com

The oil pump moves the engine oil from the oil pan into the oil filter where it gets cleaned from all the foreign bodies and then passes through the central pipe of the oil filter and into the oil gallery where it will get distributed to the moving parts of the engine that need lubrication.

Should You Pre-fill an Oil Filter?

Should you pre-fill an oil filter or not. That is the question. And to be honest, it is pretty much a controversial one. There is no correct answer that will apply to all oil filters. You will have to find the answer on the oil filter installation manual. On those installation instructions, you might see a step where it says that you shouldn’t pre-fill your oil filter.

How Oil Filter Functions

The biggest problem of pre-filling an oil filter is not the pre-filling itself, it is how it’s done. If you look at an oil filter, you will see that it has one main hole in the center of the filter and many small holes on the sides. Most people pre-fill the oil filter by pouring oil in the center hole. That is not the correct way to do it. When attached to the oil gallery, the oil enters through the small holes and goes into the filter media which is located behind those small holes. You should always pour the oil into the small holes so the oil can get straight to the filter media to get cleaned.

Can I Change The Oil Filter Without Draining Oil?

If you did an oil change and for some reason, you didn’t change the oil filter, you can change the oil filter without draining the oil. Even though on most cars the oil filter is located on the bottom of the vehicle, you can still just remove the oil filter without losing too much oil. How much oil is in the oil filter? You will only lose the oil that is inside the oil filter at that point of time which is around 0,5 liter or 1 pound.

Before you take your old filter out, you can place a draining pan underneath and collect the oil. I personally wouldn’t use that oil because it was in a dirty filter. I would just change the oil filter with a new one and then see how much oil I lost and add new oil.

Can You Take The Oil Filter Off First?

If you are doing an oil change on an engine that has the oil filter on the bottom of the vehicle, it doesn’t make any difference if you take the oil filter off first. It only makes a difference, and to be more precise, it is recommended that you take the oil filter first if the oil filter is located on top of the vehicle. If you have an engine with oil filter that sits on top of the engine, remove the oil filter first so you can get all the oil out once you remove the drain pan screw. Otherwise, you will still have dirty oil in the oil filter.

Can I Use a Fuel Filter as an Oil Filter?

Can you use a fuel filter as an oil filter? No, you cannot and no you shouldn’t use. It is impossible to use a fuel filter as an oil filter because you won’t be able to install it. Even if you somehow manage to install it, there is a big difference between the fuel filter and oil filter.

They both perform the same task which is to clean fluids from their impurities. But, one works with fuel and the other one works with oil. Their filter media is built differently and they would just not catch the impurities.

Are Cheaper Oil Filters Okay?

There are many car enthusiasts that will advise you not to use a cheap oil filter. I mean, how cheap are we talking about? There are oil filters on amazon from $3 to $450. I would certainly not buy the cheapest one, as well as the most expensive one. There are some decent oil filters in the $20-$30 price range on amazon.com.

You can always consult with your mechanic, or if you are changing your oil at home, just test different oil filters. Get a cheap one and drive your vehicle for 1000-2000 miles and then change it. See how it will perform. But, if you stay in that $20-$30 price range, you should be good to go for 3000 miles.

What Is The Best Oil Filter Wrench

Changing an oil filter without a wrench is nearly impossible. Of course you can improvise, but you risk damaging your oil filter. After installing the new oil filter, you should tighten it so it doesn’t fall off while driving. To do so, you can get all kinds of tools and try to tighten it but you might dent it or tear a hole in it.

For this operation, I have a Lisle 63600 oil filter wrench that I got from amazon. You can order a different size depending on your oil filter. The best thing is that it is kind of great if your oil filter is in a tight space.

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