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LAST UPDATED:  May 5, 2021

Best Oil Stop Leak Additives: Protect Your Fuel System

Fixing an oil leak can be quick and easy thanks to oil stop leak additives.

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PUBLISHED ON May 5, 2021

OUR QUICKLIST

Oil stop leaks are designed to stop and seal leaks caused by general wear and tear in your vehicle's engine. Over time, the engine will start to degrade, and you will have to repair it. The good news is that a high-quality oil stop leak is a relatively easy solution for certain issues. It can stop leaks as well as prevent them from occurring. There are many options available in stores and online, so it can be challenging to choose the right one. Check out the list below for some of the top options currently available.

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All of our reviews are based on market research, expert input, or practical experience with most products we include. This way, we offer genuine, accurate guides to help you find the best picks.

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Benefits of Oil Stop Leak

  • Protect the seals. Over time, the seals on the engine can harden and dry, which is the main cause of oil leaks. An oil stop leak can treat the rear main seal as well as the head gaskets so they regain their flexibility. This will prevent the oil from leaking.
  • Protect your vehicle and the environment. Oil leaks can be costly, and they're not good for the environment. They can also cause problems with your vehicle. Constantly replacing your oil can add up over time, and your engine won't perform as well.
  • Avoid the mechanic. You may choose to visit your local garage if your vehicle is leaking oil. It can be costly to pay for the diagnosis as well as the labor costs. You will save a lot of money if you choose to fix the oil leak on your own.

Types of Oil Stop Leak

Particle-Clogging Formulas

Initially, motor oil leak sealers were designed to clog the hole where oil was escaping. Each company had its own way of doing this—some of the earliest formulas used ground peanut shells as a block. The ground particles would flow to the leak and clog the area to save oil. The problem with these particles (as well as formulas that use sawdust, aluminum shavings, and other additives) is the long-term effects on a motor. They increased engine wear and would eventually do more harm than good.

Absorbent Formulas

The best engine oil stop leak additives you can buy are made to absolve into all the seals in the engine. Since these formulas do not have engine clogging particles, they don't come with the same harmful effects. The solvents expand and rejuvenate the gaskets and components to their original size and flexibility, so any leaks caused by gaps or deteriorated seals will once again be closed. Older formulas used petroleum distillates to achieve this result. Newer stop leak oil treatments use different chemicals as the distillate can further deterioration in the engine. 

Top Brands

ATP

One of the most recognizable names in the automotive field is ATP. It first started in a Chicago plant back in 1955. Since then, it has gone from selling replacement transmission parts to producing a large selection of filter kits, repair kits, cables, flywheel and ring gears, cabin air filters and chemicals. The ATP AT-205 is a favorite among consumers.

Bar’s Leaks

One company that has been focused on helping customers be their own at-home-mechanic is Bar's Leaks. This U.S.-based company has over 70 years of experience with eliminating engine leaks. The company works with experts in their field to continually deliver high-level results with easy-to-use applications. The Stop Leak Concentrate is a best seller.

Lucas Oil

Forrest and Charlotte Lucas started their company in 1989 with the goal of producing high-quality lubricants and additives. Lucas Oil got its start in Corona, Calif. The couple quickly grew the company, which has established itself as a prominent fixture in the market. Lucas Oil Stop Leak is available in both gallons and quarts.

STP

Two of the best engine oil stop leak products available are Engine Stop Leak and High-Mileage Stop Leak, produced by STP. This company is headquartered in Connecticut. In the past 60 years, it has become one of the most trusted names in automotive care. 

Oil Stop Leak Pricing

  • Under $25: To test out whether your issue can be fixed with oil stop leak, you should invest in the smaller options. For under $25, you can get any of the best engine oil stop leak additives in small quantities like 8 ounces and 24 ounces.
  • $25 and up: For continued protection, most oil stop leak additives are available in bulk quantities. This can include gallons, packs of 32 ounce containers, or even bundles of gallon containers. Larger quantities are a good option if you know your issue can be fixed with an additive.

Key Features

Plasticizers

Since the most common cause of an oil leak is gaps between the various seals, having a stop leak additive that rejuvenates the seals is essential. This is usually a chemical process that will bring cracked rubber pieces back to their original sizes. Each company will have a different way to achieve this, but chemicals that are most effective are called plasticizers.

Petroleum Distillates

A common chemical used to revitalize gaskets is petroleum distillates. The issue with this chemical is that it can have adverse long-term effects on your engine. It can wear out parts of your fuel system while it works to fix others. Over time, this can become more expensive than the original issue. Petroleum distillates are something you want to avoid in a good stop leak additive.

Other Considerations

  • Compatibility. Possibly the most important factor when considering an oil stop leak is whether or not it’s compatible with your vehicle. Some formulas will not be able to work with diesel engines, and others will not be able to work with synthetic oils. Every product will list the types of engines and fuel system they're compatible with.
  • Efficiency. For an engine oil stop leak to be cost efficient will depend on how much additive is required to add and how long it lasts. Additives that require a smaller amount to be mixed with your engine oil will be more efficient long term. An oil stop leak that will keep your seals revitalized for more extended periods will also save you money in the long run. 
  • Activation. Allowing your engine oil stop leak to activate fully is essential to fixing leaks. The additives will start to activate once added into the engine oil, and usually, they require a few hours. However, even after sitting for the required amount of hours, the solution may need to run through your fuel system for 100 or more miles to reach its full potential.

Best Oil Stop Leaks Reviews & Recommendations 2021

Best Overall

Lucas Oil is known for making reliable products. If you're looking for an oil stop leak that works without costing too much, they have the perfect solution. The 10278 Oil Stop Leak is excellent for stopping leaks and boosting your performance. 


This product does not contain any harmful solvent or any corrosive properties. That means using this product won't have any long-term effects on your engine. It's the only additive that actually improves your engine's performance. The successful resealing of your fuel system will reduce engine noise and oil consumption. 


While some additives can dilute your oil, Lucas manages to increase oil pressure, which is how you'll see your performance boost. Similar to other stop leaks, Lucas uses chemicals to recondition deteriorated seals. It is compatible with all types of engine oils, including full synthetic oils. Lucas is a financially smart option that consistently gets great engine oil stop leak additive reviews.


Much like all of the products on our list, Lucas Oil Stop Leak Additive isn't going to be able to fix every issue. Some holes are too big for the revitalized gaskets to seal correctly. Depending on what kind of seal issue you have, expanding the gaskets may have an adverse effect. Also, Lucas isn't compatible with diesel engines.

Best Overall
Lucas Oil 10278 Engine Oil Stop Leak

Lucas Oil is known for making reliable products. If you're looking for an oil stop leak that works without costing too much, they have the perfect solution. The 10278 Oil Stop Leak is excellent for stopping leaks and boosting your performance. 


This product does not contain any harmful solvent or any corrosive properties. That means using this product won't have any long-term effects on your engine. It's the only additive that actually improves your engine's performance. The successful resealing of your fuel system will reduce engine noise and oil consumption. 


While some additives can dilute your oil, Lucas manages to increase oil pressure, which is how you'll see your performance boost. Similar to other stop leaks, Lucas uses chemicals to recondition deteriorated seals. It is compatible with all types of engine oils, including full synthetic oils. Lucas is a financially smart option that consistently gets great engine oil stop leak additive reviews.


Much like all of the products on our list, Lucas Oil Stop Leak Additive isn't going to be able to fix every issue. Some holes are too big for the revitalized gaskets to seal correctly. Depending on what kind of seal issue you have, expanding the gaskets may have an adverse effect. Also, Lucas isn't compatible with diesel engines.

Best Value

What is the best engine oil stop leak? Look no further than the AT-205. This universal oil additive works incredibly fast and covers the widest range of fuel systems. Plus, the product is surprisingly cost effective when used with smaller oil leaks. ATP makes the most comprehensive oil stop leak available. This product works with both gasoline and diesel engines. It is also compatible with all oils, including conventional, synthetical, and fully synthetic. It even stops leaks in other systems like transmission, hydraulic, and power steering systems. 


This product is the best engine oil sealer. This is due to ATP's focus on revitalizing the rubber seal throughout the engine. The formula uses plasticizers to reshape and fix the rubber-based gaskets chemically. This chemical works great, and it is the same substance used to make the rubber flexible in the first place. ATP guarantees that AT-205 will start working in just five hours. You need to pour it in with the engine oil—be sure to follow the correct measurements. You can add it at any time in between oil changes without prep work. 


While the formula works excellent at rejuvenating rubber, it isn't perfect for every oil leak situation. ATP has the possibility of thinning out your oil. This depends on what type of oil you use, but thinner oil can cause issues such as lower performance and worse gas mileage. It's also possible for this product to produce blue smoke. 

Best Value
ATP AT-205 Re-Seal Stops Leaks

What is the best engine oil stop leak? Look no further than the AT-205. This universal oil additive works incredibly fast and covers the widest range of fuel systems. Plus, the product is surprisingly cost effective when used with smaller oil leaks. ATP makes the most comprehensive oil stop leak available. This product works with both gasoline and diesel engines. It is also compatible with all oils, including conventional, synthetical, and fully synthetic. It even stops leaks in other systems like transmission, hydraulic, and power steering systems. 


This product is the best engine oil sealer. This is due to ATP's focus on revitalizing the rubber seal throughout the engine. The formula uses plasticizers to reshape and fix the rubber-based gaskets chemically. This chemical works great, and it is the same substance used to make the rubber flexible in the first place. ATP guarantees that AT-205 will start working in just five hours. You need to pour it in with the engine oil—be sure to follow the correct measurements. You can add it at any time in between oil changes without prep work. 


While the formula works excellent at rejuvenating rubber, it isn't perfect for every oil leak situation. ATP has the possibility of thinning out your oil. This depends on what type of oil you use, but thinner oil can cause issues such as lower performance and worse gas mileage. It's also possible for this product to produce blue smoke. 

Honorable Mention

Liqui Moly offers a versatile anti-leak product that can be used on all diesel and gasoline engines. The fluid works by cleaning and regenerating rubber and plastic transmission seals, and consequently prevents oil stains from forming under the vehicle. The sealing action will last for about 370 to 500 miles, which gives you enough time to drive to a service station and get the leak fixed.


The fluid improves engine oil stability at high engine speeds and its viscosity at high temperatures. It also improves engine performance by preventing excessive wear on transmissions, pumps, and compressors. The product is recommended for all manual and auxiliary transmissions. 


Unfortunately, the product isn’t compatible with motorcycles with wet clutches. It’s also not suitable for vehicles with automatic transmissions, which limits its use to older vehicles and heavy-haul tractors with auxiliary transmissions.

Honorable Mention
Liqui Moly Oil Leak Stop

Liqui Moly offers a versatile anti-leak product that can be used on all diesel and gasoline engines. The fluid works by cleaning and regenerating rubber and plastic transmission seals, and consequently prevents oil stains from forming under the vehicle. The sealing action will last for about 370 to 500 miles, which gives you enough time to drive to a service station and get the leak fixed.


The fluid improves engine oil stability at high engine speeds and its viscosity at high temperatures. It also improves engine performance by preventing excessive wear on transmissions, pumps, and compressors. The product is recommended for all manual and auxiliary transmissions. 


Unfortunately, the product isn’t compatible with motorcycles with wet clutches. It’s also not suitable for vehicles with automatic transmissions, which limits its use to older vehicles and heavy-haul tractors with auxiliary transmissions.

Honorable Mention

This engine oil additive offers a simple solution for anyone who doesn’t have the time or money to drag their vehicle to a professional to fix stubborn engine oil leaks. The fluid is formulated with a sophisticated polymer sealing additive that creates a shield around the seal to protect it from wear caused by high temperatures and harsh conditions. It works to revitalize dry, shrinking rubber gaskets seals to make them soft and flexible. 


With a dual-action formula, the product also goes to work on restoring the engine’s performance by cleaning the internal parts, reducing friction, and increasing horsepower. You should expect to see the results after driving for about 250 miles or three days after application. Installing it is relatively easy as long as you take care not to overfill it. 


However, if you have an old engine, this product may not have enough punch to seal the damage. If it works, it will reduce the leak to a slight drip. 

Honorable Mention
Bar’s Leaks Engine Repair

This engine oil additive offers a simple solution for anyone who doesn’t have the time or money to drag their vehicle to a professional to fix stubborn engine oil leaks. The fluid is formulated with a sophisticated polymer sealing additive that creates a shield around the seal to protect it from wear caused by high temperatures and harsh conditions. It works to revitalize dry, shrinking rubber gaskets seals to make them soft and flexible. 


With a dual-action formula, the product also goes to work on restoring the engine’s performance by cleaning the internal parts, reducing friction, and increasing horsepower. You should expect to see the results after driving for about 250 miles or three days after application. Installing it is relatively easy as long as you take care not to overfill it. 


However, if you have an old engine, this product may not have enough punch to seal the damage. If it works, it will reduce the leak to a slight drip. 

Honorable Mention

Depending on your situation, this additive can either fix your leak on the first try or not at all. When it is effective, however, it works amazingly well. BlueDevil does not include petroleum distillates, so it is in no way harmful to your engine or its components. This oil stop leak's top components make it quite effective and it delivers an enhanced seal. It is also completely safe for people and the environment. 


One thing that makes BlueDevil stand out is its promise to permanently repair damage to shrunken or hardened seals. This is not to say that you'll never experience a leak again, but it is accurate as far as how long the rejuvenating effects will last on your seals.


While this is one of the best engine oil additives to stop seal leaks, BlueDevil has some setbacks. Some customers have pointed out this formula isn't always effective with leaky gaskets, so depending on what seal you're having problems with, this might be an issue. While it does work with both gasoline and diesel engines, BlueDevil is not the best choice for synthetic oils. 

Honorable Mention
BlueDevil Oil Stop Leak

Depending on your situation, this additive can either fix your leak on the first try or not at all. When it is effective, however, it works amazingly well. BlueDevil does not include petroleum distillates, so it is in no way harmful to your engine or its components. This oil stop leak's top components make it quite effective and it delivers an enhanced seal. It is also completely safe for people and the environment. 


One thing that makes BlueDevil stand out is its promise to permanently repair damage to shrunken or hardened seals. This is not to say that you'll never experience a leak again, but it is accurate as far as how long the rejuvenating effects will last on your seals.


While this is one of the best engine oil additives to stop seal leaks, BlueDevil has some setbacks. Some customers have pointed out this formula isn't always effective with leaky gaskets, so depending on what seal you're having problems with, this might be an issue. While it does work with both gasoline and diesel engines, BlueDevil is not the best choice for synthetic oils. 

Honorable Mention

The NO LEAK Engine Oil Stop Leak is designed to remedy engine leaks caused by dried, shrunken, or hardened rear main seals. The product works by expanding and softening the rubber in the seal to restore it to its original flexible shape. The fact that the fluid is ultra-thick and sticky helps to effectively seal the leaks. 


NO LEAK is supposedly safe and compatible with all types of engines and will stop the engine from smoking. The product is also safe to use at any time, meaning that you don't need an oil change. You will find it somewhat easy to pour the fluid since it comes in a colorless bottle where one side has multiple indents that help you measure how much liquid you pour.


However, you should be careful when handling the product and remember to wear gloves—it can cause skin irritation. Moreover, you may notice that it’s only good for repairing the rear main seal and may not be effective at repairing a leaking head gasket. 

Honorable Mention
NO LEAK Engine Oil Stop Leak

The NO LEAK Engine Oil Stop Leak is designed to remedy engine leaks caused by dried, shrunken, or hardened rear main seals. The product works by expanding and softening the rubber in the seal to restore it to its original flexible shape. The fact that the fluid is ultra-thick and sticky helps to effectively seal the leaks. 


NO LEAK is supposedly safe and compatible with all types of engines and will stop the engine from smoking. The product is also safe to use at any time, meaning that you don't need an oil change. You will find it somewhat easy to pour the fluid since it comes in a colorless bottle where one side has multiple indents that help you measure how much liquid you pour.


However, you should be careful when handling the product and remember to wear gloves—it can cause skin irritation. Moreover, you may notice that it’s only good for repairing the rear main seal and may not be effective at repairing a leaking head gasket. 

Honorable Mention

Hapco's Pro-Seal features a concentrated formula that tackles leaks in the engine, transmission, differentials, power steering, gear cases, transfer cases, and more. It's easy to use and makes rubber seals more flexible and elastic. The non-clogging formula stops current leaks and doesn't contain any petroleum distillates, which can damage seals.


Pro-Seal is compatible with conventional and synthetic oils and fluids. You can add it to your vehicle's system at any time. Just make sure the vehicle is turned off and add one bottle or 1 ounce per quart to the reservoir where the leak is occurring. Then drive or operate the machinery so the fluid properly circulates. It should stop leaks within 2-5 hours. Users report that it works well and is a good way to avoid potentially costly repairs.


However, like other products on this list, it will not stop or slow the oil leak in all circumstances. According to some users, it may only stop certain leaks for a short period of time.

Honorable Mention
Pro-Seal by Hapco

Hapco's Pro-Seal features a concentrated formula that tackles leaks in the engine, transmission, differentials, power steering, gear cases, transfer cases, and more. It's easy to use and makes rubber seals more flexible and elastic. The non-clogging formula stops current leaks and doesn't contain any petroleum distillates, which can damage seals.


Pro-Seal is compatible with conventional and synthetic oils and fluids. You can add it to your vehicle's system at any time. Just make sure the vehicle is turned off and add one bottle or 1 ounce per quart to the reservoir where the leak is occurring. Then drive or operate the machinery so the fluid properly circulates. It should stop leaks within 2-5 hours. Users report that it works well and is a good way to avoid potentially costly repairs.


However, like other products on this list, it will not stop or slow the oil leak in all circumstances. According to some users, it may only stop certain leaks for a short period of time.

Honorable Mention

CD-2 "guarantees" that its product will stop oil leaks in your vehicle. The formula is designed to stop common engine leaks within 300 miles after application. Simply pour the bottle into a 3-6-quart engine oil crankcase, and then drive as you normally do. The product works with all grades of motor oil, and added detergents keep the oil cleaner for a longer period of time.


This product also contains anti-wear and friction modifiers to further protect the engine. Users report that it is very effective and seals leaks when other products can't. It does a good job of stopping minor oil leaks in older vehicles with old gaskets and seals that are no longer flexible and have lost their ability to maintain a seal.


However, repeat applications may be necessary. It is not an instant fix, and you must run the vehicle or machine for a little while after the application for it to work. Also, it won't repair cracked or broken seals.

Honorable Mention
CD-2 Stop Leak for Engine Oil

CD-2 "guarantees" that its product will stop oil leaks in your vehicle. The formula is designed to stop common engine leaks within 300 miles after application. Simply pour the bottle into a 3-6-quart engine oil crankcase, and then drive as you normally do. The product works with all grades of motor oil, and added detergents keep the oil cleaner for a longer period of time.


This product also contains anti-wear and friction modifiers to further protect the engine. Users report that it is very effective and seals leaks when other products can't. It does a good job of stopping minor oil leaks in older vehicles with old gaskets and seals that are no longer flexible and have lost their ability to maintain a seal.


However, repeat applications may be necessary. It is not an instant fix, and you must run the vehicle or machine for a little while after the application for it to work. Also, it won't repair cracked or broken seals.

Honorable Mention

SealLube can be used to stop leaks related to gas and diesel engines, automatic and manual transmissions, power steering, rack and pinion, differentials, and hydraulic systems. It can be used on your vehicle, tractor, marine engine, heavy equipment, etc. The formula revitalizes leaking hard rubber seals, prolongs their life, restores tensile strength, and prevents the seals from leaking in the future.


One 8-ounce bottle treats up to 8 quarts, and it's compatible with conventional and synthetic oils. Simply add it to the fluid reservoir, crankcase, or oil sump pump while the vehicle or machine is turned off. Next, start the engine and drive the vehicle or operate the machinery as you normally do. It does not have any petroleum distillates in the formula, so you can safely use it over and over again. The product is made in America and comes with a 100 percent money-back guarantee if you experience any issues.


However, it may simply slow down a leak instead of stop it completely, depending on the circumstances. It also doesn't work on all leaks, and it is often just a temporary solution.

Honorable Mention
SealLube

SealLube can be used to stop leaks related to gas and diesel engines, automatic and manual transmissions, power steering, rack and pinion, differentials, and hydraulic systems. It can be used on your vehicle, tractor, marine engine, heavy equipment, etc. The formula revitalizes leaking hard rubber seals, prolongs their life, restores tensile strength, and prevents the seals from leaking in the future.


One 8-ounce bottle treats up to 8 quarts, and it's compatible with conventional and synthetic oils. Simply add it to the fluid reservoir, crankcase, or oil sump pump while the vehicle or machine is turned off. Next, start the engine and drive the vehicle or operate the machinery as you normally do. It does not have any petroleum distillates in the formula, so you can safely use it over and over again. The product is made in America and comes with a 100 percent money-back guarantee if you experience any issues.


However, it may simply slow down a leak instead of stop it completely, depending on the circumstances. It also doesn't work on all leaks, and it is often just a temporary solution.

Honorable Mention

The STP High Mileage Oil Treatment + Stop Leak is designed to be used with every oil change and is perfect for use on cars, light trucks, and SUVs. This 15-fluid-ounce bottle is a good option for vehicles with more than 75,000 miles on the odometer. It rejuvenates seals and gaskets so they don't leak or smoke.


The high-viscosity formula includes anti-wear agents and is designed to reduce metal-to-metal friction. This is due to the thick formula, which provides more protection between the moving engine parts. Users report that it noticeably slows leaks down and reduces burnt oil smells. Overall, it's an inexpensive and effective fix.


One downside is that the product is so thick, it can take a while to pour, particularly in cold temperatures. Also, like similar products, it does not stop all leaks, and it may lose its effectiveness before your vehicle is ready for its next oil change.

Honorable Mention
STP High Mileage Oil Treatment, Formula for Cars & Truck, Stop Leak

The STP High Mileage Oil Treatment + Stop Leak is designed to be used with every oil change and is perfect for use on cars, light trucks, and SUVs. This 15-fluid-ounce bottle is a good option for vehicles with more than 75,000 miles on the odometer. It rejuvenates seals and gaskets so they don't leak or smoke.


The high-viscosity formula includes anti-wear agents and is designed to reduce metal-to-metal friction. This is due to the thick formula, which provides more protection between the moving engine parts. Users report that it noticeably slows leaks down and reduces burnt oil smells. Overall, it's an inexpensive and effective fix.


One downside is that the product is so thick, it can take a while to pour, particularly in cold temperatures. Also, like similar products, it does not stop all leaks, and it may lose its effectiveness before your vehicle is ready for its next oil change.

Tips

  • Consult a mechanic if the problem isn't solved after you use an oil stop leak. If your engine loses a lot of oil, it can sustain a lot of damage. It's vital that you diagnose and fix the problem sooner rather than later.
  • Read the product description to make sure you use the proper amount when you mix the oil stop leak with your oil.
  • Determine whether your vehicle uses conventional or synthetic oil before making a purchase. While many can be used with different types of oils, it's important that the product is compatible with your particular oil.
  • Some oil additives include harmful chemicals. These additives can do long-lasting damage to your vehicle's engine. Avoid any oil stop leaks that use petroleum distillates and look out for products that are certified by the EPA.

FAQs

Q: How do I use oil leak stop fluid?

Oil stop leaks are easy to use. Simply mix it with the oil you traditionally use in your car or truck. Make sure to properly measure the amount you need. You can find this information on the container of the stop leak fluid.

Q: Is oil stop leak bad for your engine?

Some old-fashioned oil stop leaks were not good for engines. Modern technology has caused the creation of better formulas, so today's products should work just fine. However, if you use the wrong oil stop leak, it can cause engine damage, so make sure to do your research and choose the proper additive.

Q: What if the oil stop leak doesn’t work?

Oil stop leaks are a great solution, however, they aren't designed to fix all issues. Should you use a product and don't notice an improvement, take your vehicle to a mechanic so he can properly diagnose the problem.

Q: Can oil stop leak be used instead of going to a mechanic?

Maybe. That depends on what is causing the oil leak. Oil stop leaks are designed to revitalize gaskets and seals to minimize gaps that cause leaks. However, if you have a large hole or a lot of engine damage, an oil stop leak will not solve the problem.

Final Thoughts

If you’re looking for universal protection, then Lucas Oil 10278 Engine Oil Stop Leak is the best engine oil stop leak product on the market. 

Customers who want to stop leaks and save money should use ATP AT-205 Re-Seal Stops Leaks.