How do oil filters work?
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How Oil Filters Work (Ultimate Guide)

Clean oil is extremely important when it comes to running a car’s engine. Therefore an oil filter is a necessity. But how do oil filters work and why do we need clean oil? Well, oil has a number of important uses such as the following:

  • Transferring heat away from the combustion area
  • Sealing gaps between piston rings and cylinder walls
  • Absorbing contaminants such as dust and other airborne impurities

Back in the infancy of motoring, oil filters weren’t required. Mainly for the fact they didn’t know to use them, but also because the oil changed frequently anyway, due to it burning and being of poor quality in the first place.

A bit later, metal meshing was used to block larger objects from entering, but it wasn’t until the 1920s when the ‘Purolator’ was invented. The Purolator, or ‘pure oil later’ was invented by Ernest Sweetland, and these and filters like it were offered as optional and aftermarket products for years until the 1950s where the filter became standard on the majority of cars.

Soon after, canister type filters were replaced by spin-on filters, and these are now used almost universally today, allowing for 10,000 miles between each service for most cars.

How do oil filters work?

We’ve established that oil filters remove impurities from the oil, but how do oil filters work? Well, the oil enters the filter via the outside of the gasket – sometimes called the tapping plate – before flowing through a several filter mediums. Once the oil is cleansed, it flows back up the centre though a steel tube. It’s stopped from flowing backwards due to an anti-drain back valve.

But what happens when the oil is cold and too thick to flow through the filters? A relief valve is used, which allows oil to bypass the filters to keep the engine lubricated while the oil warms up to operating temperature. There are also end discs made of metal or a fibre which stop unfiltered oil returning back into the engine via the steel tube when the valve isn’t in use.

Are there different types of oil filters?

Now we’ve established how oil filters work, let’s discuss the different types of oil filters available.

You get what you pay for when it comes to oil filters, and usually you’ll find yourself with four filter options: standard oil filters, high-performance oil filters, racing filters, and synthetic filters.

Standard oil filter

As explained above, these very simply cleanse the oil under normal everyday circumstances for road cars.

High performance oil filters

These are built to a higher quality to withstand the damage that could occur during a hard race such as debris. Some even have rolled threads so they are more easily installed, and stiffer baseplates so they don’t flex under extreme conditions.

Racing oil filters

As racing cars have much thinner oil than road cars and are used under very different conditions, they’re filters are simplified for ease. Their internals are however engineered to resist high temperatures and to allow oil through with low levels of restriction, and their filter medium is designed to trap even smaller impurities to allow the engines to last in endurance races, for example.

Synthetic oil filters

In synthetic oil filters, the filter medium, which is usually made of a pleated paper-like material, is replaced with a synthetic material. These types of filters can filter oil for longer and to a higher extent, and therefore don’t have to be replaced as usually as the standard types. Their casing is usually larger with a larger oil volume, and will last usually from 7,000 to 25,000 miles.

So now you know what types of oil filters are available, how an oil filter works, and what to choose depending on your uses. Just remember that it’s always best to choose the OEM oil filter that’s listen in your car’s user manual, and remember to change them at the recommended intervals.

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Written by Alex Harrington

Alex started racing at a young age so certainly knows his way around a car and a track. He can just about put a sentence together too, which helps.

He has a great interest in the latest models, but would throw all of his money at a rusty old French classic and a 300ZX.

Contact: [email protected]

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