A Comprehensive Guide to Choosing the BestStop Leak Oil Additives for Your Engine

By now you’ve heard of oil additives and all the ‘magic’ they can entail. But what you may have not heard of yet is stop leak oil additives.

Although still technically an oil additive since it is ‘added’ to your car’s oil, rather than trying to improve gas mileage or something similar, these compounds are specifically formulated to stop oil leaks that are coming from your engine.

There are a few different types of these stop leak additives and we’ll dive into all of them and which are best and when to use or not use them.

Overall these are not meant to be the equivalent of a mechanic fixing your oil leak problems, but they do have their place and can save you a ton of money as oil leaks always lead to expensive repairs, and even blow motors! So this is all quite serious stuff.

What are Stop Leak Oil Additives?

Stop leak oil additives are a bit different than the other oil additives you might be familiar with in that they are doing one specific thing rather than many, they work to stop oil leaking from your engine.

Since they are working to stop oil leaks rather than increase the lubrication qualities of your motor oil, they are manufactured very differently than other oil additives. And they’re often made from either natural oil based products, or synthetically manufactured compounds and chemicals.

Which you use really depends on the size of your wallet. The synthetic stop leak additives are much pricier than the natural oil based ones. But they also work a lot better and they’re safer long term for your car. So they are worth the investment in our opinion.

All types of these additives work by somehow expanding the engine’s gaskets, seals, and O-rings through the use of science. There are a few ways they do this and each additive is different depending on the manufacturer. Some of the most commonly used types of stop leak oil additives include:

Petroleum-based additives: These additives are made from petroleum compounds and are the cheaper type of additive compared to synthetics. They work by conditioning the rubber or plastic parts in your engine so that they become softer and seal more properly. These were the first type of stop leak oil additives and they still work well, but they also sometimes cause more problems so we recommend the synthetic formulations over this type of additive.

Synthetic-based additives: These are the best type of stop leak oil additives marketed today. They work on a variety of problems and can target specific parts of your engine like valve cover leaks or rear main seal leaks. They are more expensive than the other types we’re covering here, but the added cost is worth it.

Seal conditioners: These are more long term maintenance products rather than a short term leak fix. These types of additives help keep all the non metal parts of your engine working like new by keeping them pliable so they never crack or shrink and cause leaks.

Anytime you’re using stop leak oil additives, it is critically important to follow the manufacturer’s instructions carefully, they’re printed on the can for a reason. Use too much additive and it can end up eating away at the very parts it’s meant to protect. Use the wrong type and you’re probably just throwing your money down the drain!

When to Use Stop Leak Oil Additives?

Stop leak oil additives are typically used in situations where there is a minor oil leak in an engine or other lubrication system. These additives are designed to temporarily seal or reduce leaks by swelling and softening the seals and gaskets, effectively slowing down or stopping the oil leakage.

Here’s a few instances that these additives are perfect for:

Minor oil leaks: If you notice a small oil leak in your engine or other lubrication system, and it is not causing significant problems or affecting the overall performance, a stop leak additive can be used as a temporary solution. Temporary is the important word here! You’ll need to see a mechanic sooner or later.

Aging seals and gaskets: Over time, the seals and gaskets in you car’s engine will deteriorate or shrink just due to age, leading to oil leaks. Stop leak additives can help soften and swell these aging seals, potentially reducing or stopping the leakage.

Small cracks or punctures: Sometimes small cracks or punctures may develop in the engine seals or gaskets due to the parts being badly manufactured, or just plain old. Stop leak additives can temporarily fill these tiny gaps, minimizing the leakage until a permanent repair can be arranged with your mechanic.

Some other obvious signs there is a problem are:

  • Oil stains on your driveway or garage floor
  • A decrease of oil levels in your car’s oil reservoir
  • An increase in oil consumption
  • The engine oil warning light turning on

It’s important to note that stop leak oil additives should be used as a temporary solution and not as a substitute for proper repairs. If you’re experiencing significant oil leaks or if the additive doesn’t solve the problem, it’s recommended to have a qualified mechanic inspect and repair the underlying issue.
Always follow the instructions provided by the manufacturer of the specific stop leak oil additive you choose, as different products may have varying application methods and usage recommendations.

How to Choose the Right Stop Leak Oil Additives

Right now, even though these are very specialized additives, there are still a tom of different brands and formulations available. It can literally sometimes feel overwhelming if you have no idea on what you need or are looking for.

But it isn’t rocket science either. You just need to understand if the leak is even originating from your engine and an additive can help alleviate the situation. Once you figure that out, the next step is to deduce where and how severe the leak is.

Another important consideration is how old your car’s engine is and how badly you beat it over the years. There are additives that are meant to work specifically for older cars, so look for one that specifies that’s what it’s for.

You should also be aware of what type of driving you do all day, and what kind of driver you are. Are you an aggressive driver and you’re doing city miles, or is it all open roads and barely stopping? They’re all important to know.

Types of Stop Leak Oil Additives: We’ve already mentioned there are many types of stop leak oil additives, but now we’ll go more in depth about what each one is and when they should be used.

Petroleum-based additives: These are the type of stop leak oil additives you’ll find at places like Walmart. They’re often cheap and can be found almost anywhere as they were the first stop leak additives of their kind. They’re made using petroleum and work well for small leaks that you need some time to get repaired, but they’re not really good for long term use as they can mess with other non metal parts of the engine.

Synthetic additives: These are the most expensive of the different types of stop leak additives and tend to target specific issues, such as leaks in valve covers or rear main seals. They’re also a safer option than the petroleum based additives as they don’t cause damage to other engine parts in the way they do, which is also why we always recommend synthetic additives to all our readers.

Seal conditioners: A tad different in use than the two previous additives, these additives work to keep your plastic and rubber engine parts from drying out and cracking or deforming, all major causes of engine oil leaks. Although they can possibly help short term, they’re more meant to be a preventative measure against leaks and are a smart addition to ageing cars.

Cooling system leak stoppers: Although not technically an engine oil additive, they’re worth mentioning just in case. These are what you use to stop minor leaks in your car’s radiator, heater core, or water pump, they are never meant to be added to your motor oil!

So as you can see, there really is a stop leak oil additive for almost any car or leak problem. You just need to figure out which is best for your personal situation.


Stop leak oil additives are a great way to stop small pesky leaks that can be making your driveway ugly, but that doesn’t mean they should be used to fix major problems, or even long term.

Rather these additives are meant to give you time to find a good mechanic that can tell you what’s really going on with your engine and then get the root problem fixed.

Or a cheap and efficient way to rejuvenate old parts like your seals, gaskets, and O-rings that have begun leaking simply because they are old and have lost their elasticity.

But of course the best way to make sure you never get an oil leak is to make sure you are following a regular maintenance schedule and having your car serviced by a professional mechanic who can spot problems before they become something more serious.


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