Are oil leak-stop additives bad for the engine of a car?

Finding a leak anywhere in your car is a problem and an annoyance, but it is even more of an issue when you are short of the money required to replace a damaged seal. Inevitably, we all look for more convenient and affordable solutions.


Oil leak-stop additives fit this description – providing a quick fix for leaks so that you can quickly get back on the road again. However, could oil additives be bad for your engine? To answer this question, we need to explore what oil leak-stop additives actually are and when it is appropriate to use them.

What are oil leak-stop additives?

Due to a number of factors, including the mileage and age of the car, the engine gaskets and seals sometimes become hard and inflexible and reduced in size. This effectively creates holes in the engine and as a result oil can leak out. The oil additives are designed to lessen the amount of oil that can leak past seals that have degraded in this way. Oil leak-stop additives are typically non-solvent formulations that combine chemicals to re-soften the gasket, ceramic particles and fibres to plug the gap, and sometimes sodium silicate particles that melt and seal it in place.

When can you use an oil leak-stop additive?

Before we complain about leaks appearing in our cars, we should recognise that they usually arise because we haven’t kept up a regular servicing routine. If you keep putting off renewing your coolant fluids instead of following the recommended schedule the system is likely to become corroded sooner or later. This is usually the circumstances when oil leak-stop additives will successfully fix the leak.

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Be aware that many oil additives only provide a quick, temporary fix for small leaks. One-off emergency use will not necessarily do your engine any harm, but repeated use can do more harm than good. After a while excess additives often settle and clog up the system. Also, leak-stop additives aren’t a magic wand that works everywhere: for example, they can’t stop leaks around rotating components such as inside a pump (they are more likely to stop the pump). Similarly, they cannot fix leaks near the front seal or rear main engine seal. When you finally replace your coolant, temporary seals usually wash out at the same time. Some products are formulated to provide “permanent” seals, but you should still keep your fingers crossed.

So, what is the best way to fix a leak?

Replacing a seal involves a lot of costly labour, so look after them! In our experience, having those coolants checked and changed frequently is the best way to prevent leaks or to stop them getting bigger. Use our online garage-locator to contact your local Protyre and arrange for our experienced fitters to check your fluids and investigate whether you already have a leak that needs remedying.

Talk to the experts

With over 100 garages across the UK, Protyre are always nearby with help. Our garages only stock original and top-quality components, including Pirelli and Bridgestone tyres and our tyre professionals are also on hand to provide free advice. You can also book a free tyre check online.

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About the author

Lindsay-Marie Gorman

Lindsay is a Digital Marketing Content Creator for Protyre and joined the company in March 2020. After gaining a ...

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