Magnetic trap on oil filters - Do they really work or is it just a quack remedy?

In recent times, a growing number of service centres and workshops are advising owners to fit a magnetic trap on (or under) the oil filter, which is said to trap and isolate metal particles within your engine oil, thereby improving the life expectancy of the oil, and thus your engine.

In most cases, these magnets cost just under RM 100 and are reusable, but do they work? Or, are these magnet traps just a quack remedy that does nothing? After all, if they’re so effective, why don’t manufacturers just install them from the factory? Well, they don’t, and here’s why.

The working principle is sound, but it’s not doing anything different…

Whilst yes, the working principle is sound – a magnet will always attract metal – these magnet traps are not doing anything that the engine oil filter isn’t already doing.

In an internal combustion engine, oil stored in the sump is pumped through the oil filter and circulated through a maze of oil passageways to properly lubricate every moving component in the engine, before it returns to the sump.

Also read: Is synthetic engine oil bad for older cars?

Any metal or debris in the oil, measuring just microns in size, is trapped by the filter and kept out of circulation.

Therefore, placing a magnet here isn’t really going to do anything, because most of these impurities get stuck on the filter element, and stay there due to the positive pressure of the oil passing through it.

Also read: Are you using the WRONG engine oil for your car?

Weak magnets and flawed demonstrations

Plus, there is little data on just how strong or effective these magnets are, which casts further doubt on their effectiveness. Now we’re not saying some metallic components won’t be retained by the magnet, but these metals or debris were already trapped by the filter in the first place, so what’s the difference?

Companies that sell magnet traps will often showcase the above demo, showing metallic bits sticking to the magnet which would otherwise fall to the base without the magnet.

This demonstration is as flawed as it is silly, for just one reason. Oil isn’t freely suspended in your oil filter as it is in the glass jar.

To properly lubricate your engine properly, oil pressure ranges between 10 PSI at idle, to over 60 PSI at high revs – that’s nearly double the tyre pressure needed for a mid-sized SUV.

Combustion engines require around 25 – 35 litres of oil to be circulated through the filter in a single minute, that number rises to over 45 litres in high-performance engines.

What chance does a small magnet have at trapping microscopic metallic debris when oil is travelling at such volumes?

Conclusion – You don't need it, use only genuine engine oil purchased from autorised resellers

The most important point to note is that if these magnets are so effective at prolonging engine life, manufacturers – who want their engines to last as long as possible – would fit them from the factory, but they don’t.

Instead, what they do prescribe is timely oil changes using good quality oil and genuine replacement parts, which guarantees an engine will run smoothly and efficiently for many years.

Also read: How often should you service your car?

Removing metal and debris in the oil is exactly what an oil change is meant to do.

Additionally, if you need a flimsy magnet to trap metal particles in your oil, the appropriate question to ask is why they are there in the first place – because if you have metallic particles that the oil filter can't cope with, your engine has much bigger problems for any magnet to solve.

If your car needs maintenance work, try CARSOME Service Centre.

UPDATE, August 2023: CARSOME is now offering a RM 50 car service voucher and free 20-point inspection, available at their PJ and Ampang outlet.