Advertiser Disclosure
Leaking engine oil is a fairly common problem, especially with older cars. The leakage may seem small, even inconsequential, but there are real dangers involved in driving a car with leaking engine oil.
For one, losing oil is costing you money every time you have to top up the oil before an oil change is due. You also run the risk of oil levels dropping too low without your knowledge which can cause severe and expensive engine damage in the long-term.
We have outlined the real dangers of leaking oil in our FAQ section of this article.
Aside from the dangers of driving a car with leaking oil, this is an embarrassing problem. Leaving a nice black pool of engine oil on your host’s driveway is hardly the way to say thank you for a scrumptious dinner.
Fortunately, there are additives that you can mix with your engine oil to take care of the leaks for good. These additives are commonly referred to as ‘oil stop leak’ products.
You no longer have to deal with the embarrassment or impending danger of constant leaking engine oil ever again!
The Top 5 Best Oil Stop Leak Additives Review
There are dozens of oil additives on the market that claim to stop leaks; so finding the best one easily becomes an uphill struggle.
With a few mechanic mates, we spent the past few weeks putting the best oil stop-leak additives on the market to the test. We tested around 20 of the top-selling oil additives and ended up with what we believe are the 5 best engine oils on the market.
Check out our quick comparison table below if you are pressed for time.
Product Quick Compare
Lucas Engine Oil Stop Leak​
- Rating: 4.8 / 5
- Brand: Lucas
- Volume: 32 ounces (or 900ml)
- Model: 10278
Lucas Engine Oil Stop Leak is considered one of the best products available for preventing engine oil leaks. The unique features of this oil additive is what makes it stand out from the crowd. It’s extremely versatile, working with both engine types, is non-corrosive and unlike other additives on the market, it improves the engine performance by raising oil pressure and reducing consumption.
Lucas Engine Oil Stop Leak is a low-cost investment which rejuvenates worn down seals with ease. No more leaks, no more corrosion and definitely no more of those weird sounds coming from the engine.
Lucas Oil 10278 is compatible with all kinds of engine oil including mineral, fully synthetic, and semi-synthetic oils. This additive also works for both gasoline and diesel engines. The product is available in a variety of sizes including 1 quart, 1 gallon, and even a 55-gallon package depending on your needs.
The additive is easy to use. Simply mix into your engine oil. Use 80-percent engine oil and 20-percent Lucas oil stop leak and you should see a difference almost immediately.
The downside of this product is it may not stop leaks in vehicles with severely damaged seals. For this, you will need the expertise of a mechanic.
What We Liked
- Compatible with all oil types including mineral, semi-synthetic, and full synthetic motor oil
- Oil stop leak works for both gasoline and diesel engines
- The additive reduces engine noise
- The oil does not contain harmful additives that may corrode or damage the engine
- Rejuvenates worn gaskets and seals
- May not work in cars with severely damaged seals
What We Didn’t Like
- May not work in cars with severely damaged seals
Bar’s Leaks Grey Rear Main Seal Repair Concentrate
- Rating: 4.5 / 5
- Brand: Bar’s Leaks
- Volume: 16.9 ounces (or 500ml)
- Model: 1040
The rear main seal is expensive and difficult to repair, especially without experience. Bar Leaks has created a product specifically designed to fix stubborn engine oil leaks that occur as a result of a cracked seal.
Bar’s Leaks Grey Rear Main Seal Repair is an innovative oil leak-stop additive which repairs seals and prevents other types of leakage. The product is designed to work quickly and with ease, so there’s no need to worry about mechanics or hidden costs.
Bar’s Leaks 1040 Grey will also take care of your timing cover, cam seal, O rings, and cover seals as well as restoring your rubber gaskets to stop the leakage. The product does not contain any particle additives that may clog your oil filter.
You should begin to see results after 250 miles or three days of using Bar’s Leak 1040 and works with all oil types. This additive works for up to 6000 miles.
The main downside of this product is some users report that the results can be hit-or-miss for older engines. The reviews, however, have been mostly positive with a majority of users claiming that this oil stop leak works well.
What We Liked
- Specially formulated to repair leaks on the main rear seal
- The product also works for O rings, cover seals, rubber gaskets, timing cover, and cam seal
- Rejuvenates dry seals and gaskets to stop leaks
- Shows results within a short time
What We Didn’t Like
- Results may be hit-or-miss for older engines
Blue Devil Oil Stop Leak
- Rating: 4.0 / 5
- Brand: Blue Devil
- Volume: 8 ounces (or 237 ml)
- Model: 49499
Blue Devil is a trusted company that’s been around for a long time, so you can trust they know how to fix your car engine. Their product, Blue Devil Oil Stop Leak is among one of the best oil leak-stop additives available.
The popular oil additive contains a combination of the best ingredients designed to seal and protect your engine from current and future leaks. This product is highly praised for its compatibility with both engines (diesel and gasoline) and its guarantee to provide a permanent solution to all engine oil leaks. It is also very safe to use.
The product is formulated specifically to close up worn gaskets and seals without clogging, corroding, or wearing them. The oil works just as well for reconditioning shrunken and hard gaskets.
The odorless liquid works with most gasoline and diesel engines and will stop minor leaks in about an hour or two. Larger leaks may take up to 2 days of using BlueDevil Oil Stop Leak to resolve. You can also use this oil stop leak for gear cases, axle seals, refillable shock absorbers, gear differentials, pinion seals, and transmissions.
The main downside of this product is that it doesn’t work quite as well for severe gasket leaks. This oil stop leak is also a little more expensive than the other products covered in this review.
What We Liked
- The additive repairs minor leaks in just a few hours
- Works for most gasoline and diesel engines
- Oil stop leak covers a wide variety of leaking parts
- Does not contain additives that may corrode or otherwise harm the engine
What We Didn’t Like
- Product may not work for severe gasket leaks
- Slightly more expensive than other alternatives
No Leak Engine Oil Stop Leak
- Rating: 3.8 / 5
- Brand: No Leak
- Volume: 16 ounces (or 473ml)
- Model: Engine Oil Stop Leak
No Leak Engine Oil Stop Leak is a solution that’s guaranteed to stop engine oil leakages. The solution works by swelling the rubber in the seals and restoring them to their original state of flexibility and size. Not only is this product long lasting and simple, it’s also perfectly safe and compatible with all engine types.
No Leak 20401 is ultra-thick and sticky to help seal leaks effectively. Its properties allow the oil to restore shrunken, dried, and hardened seals that it comes into contact with. This product also stops your engine from smoking and you can add it to your engine oil at any time without necessarily waiting until you need an oil change.
No Seal 20401 is specially formulated to repair rear main seal leaks so you don’t have to go through the trouble or expense of changing the seal.
The main downside of this product is that it works exclusively to stop leaks in your seals, precisely the rear main seal. This oil additive will not help with a leaking head gasket.
What We Liked
- Affordable
- Helps to avoid replacing the rear main seal
- Rejuvenates dried, shrunken, and hardened seals
- Safe to use; no corrosion, explosions, or fire
What We Didn’t Like
- The product only works on compromised seals and does not repair a leaking head gasket
AT-205 RE-SEAL Additive
- Rating: 3.5 / 5
- Brand: ATP
- Volume: 8 ounces (or 273 ml)
- Model: AT-205
The ATP AT-205 is easy to use and works for a variety of oil leaks. You can pour the additive into hydraulic oil, engine oil, power steering fluid, or transmission fluid and the oil will find its way to damaged seals and fix the leak.
This additive doesn’t interfere with the composition of your oil so you don’t have to worry about damage to the engine or other parts. The AT-205 is compatible with fully synthetic, semi-synthetic, and mineral oils, as well as gasoline and diesel powered engines.
The product works in about five hours and will reshape and rejuvenate rubber seals and gaskets to stop leaks.
The main downside of this product is there have been reports that using AT-205 with thin oils may reduce engine performance. Speak to a professional if you intend to use the oil stop leak on mineral oil or for high-mileage vehicles.
What We Liked
- Fast-acting, stops minor leaks in about 5 hours
- Does not contain petroleum distillates that can break down rubber seals and gaskets
- Affordable
- Compatible with engine oil, hydraulic oil, power steering fluid, and transmission fluid
What We Didn’t Like
- The product may reduce engine performance when mixed with thin engine oil
Best Oil Stop Leak Buyer’s Guide
Choosing the best oil stop leak product on the market can easily get confusing given the many options available. Many of these products make large claims only to disappoint, or worse, damage your engine.
We have created this Buyer’s Guide with the safety of your car engine in mind. We will explore everything that you would need to know before buying an oil stop leak that actually works and that won’t damage your engine.
How to Buy the Best Oil Stop Leak
There are several factors that can help you to choose the best oil stop leak for your vehicle. Keep these criteria in mind while browsing the options and you can’t go too wrong with finding the right product.
Type of Oil Stop Leak Formulation
There are different types of formulations that go into creating oil stop leak products. The formulation depends on the particular manufacturer and what the additive is designed to do. There are three main formulations for oil stop leak products including:
Absorbent Formulas
Absorbent formulas are the most common in oil stop leak additives and generally provide the best results. These products are formulated with high-quality ingredients that soak into damaged seals and gaskets. The product rejuvenates these seals, restoring them to their original condition and therefore sealing the leaks.
All the products mentioned in our review are created using absorbent formulas.
Particle-clogging Formulas
Particle-clogging formulas are a little dated and were the first oil stop leak additives to hit the market. These products contain particles that fill in the gaps left by damaged seals and gaskets to seal the leakage.
This technology was rudimentary and often caused more problems than it solved, including clogging and damaging the engine.
Combination Formulation
This formula combines absorbent and particle-clogging formulas. The technology here is far more advanced than the products mentioned above. These products tend to work best for major leaks.
Efficiency
The results after applying oil stop leak products are hardly instantaneous. You can expect to drive for at least 100 miles before you see a significant improvement in your oil leaks.
Some additives work faster than others. You want an additive that works quickly so you don’t continue to leak oil while you drive.
Compatibility
It is a good idea that you first identify the source of the leakage before you buy an oil stop leak product. Some products do not work on gaskets while others are specifically designed to target certain areas such as main rear seals.
Sometimes the leak may be from the transmission, power steering, or shock absorber hydraulics so you want a product that is specially designed to work with the type of oil you intend to mix it with.
Most of these products are also compatible with gasoline and diesel engines and can be used with fully synthetic, semi-synthetic, and mineral oil. It is worth confirming that the product meets all the requirements for your car.
Possible Side Effects
Some formulations are actually harmful to your engine. Petroleum distillates and while effective in the short term, it tends to damage and wear down seals and engine parts in the long term.
Make sure that the product you are using doesn’t contain distillates and other additives that may be harmful to your engine.
All the products reviewed here pass the safety test on this account.
Oil Stop Leak Frequently Asked Questions
You may have some additional questions regarding the use of oil stop leaks. We endeavored to create a conclusive guide and have included the most frequently asked questions by customers relating to oil stop leaks.
We hope that this section will clarify anything that might have been left out in our review thus far.
An oil stop leak product, as the name implies, is a liquid formulation that is specially mixed to stop oil leaks. The product is typically mixed with engine oil or other types of oil such as transmission oil or hydraulic oil.
The quick answer is yes, oil stop leak products work for stopping most minor engine leakages. It is worth mentioning that there is a limit to what these additives can do.
As wonderful as oil stop leak additives are, even the highest quality and technologically advanced formulation will not repair serious or extensive damage to your gaskets or seals. Some types of leaks can only be repaired by a mechanic, usually involving replacing parts such as seals and gaskets.
The oil stop leak formulation helps to revitalize dry, shrunken, or damaged seals and restore them to their original condition; thus repairing the leakage. Most leaks come from worn-out rubber seals that dry out or harden with age. This process creates space where the oil may leak. Some oil stop leak products contain particles that fill in these gaps while also restoring the damaged seals.
The most common cause of leaking engine oil is damaged oil gaskets or pans. These parts are exposed to the road on the underside of the vehicle and susceptible to damage from road debris. These parts also wear over time. Bad valve seals and rings can also cause your car to leak oil. You may be able to stop the oil leak by using oil stop leak additives depending on the extent of the damage.
For the most part, driving with an oil leak may not present an immediate danger but you still want to get the problem addressed as soon as possible. The oil leak can cause extensive damage to your rubber hoses and seals, leading to further problems down the road.
Oil leaks also pose a fire hazard and could lead to sudden engine failure. Depending on the severity of the leak, you may run out of oil while driving which can lead to severe engine damage and possible engine failure. Check your oil levels regularly in case of a leak and top up as required. Get the problem fixed as soon as possible to prevent serious damage to your engine.
Conclusion
Oil additives that stop leaks have been proven to work perfectly in doing what they have been made to do. There are cases where an engine oil leak will cause the formation of smoke as the oil seeps into the combustion area. This requires that you use an additive that is also capable of preventing the formation of the said smoke (in most cases it is blue in color).
If you are new to using these types of additives, it is highly recommended that you acquire assistance in identifying the one that is best for your car as getting the wrong one could lead to more problems for your engine. Have engine problems? Have a look at our engine oil category for possible solutions.
BONUS: Watch this video on how to stop leak additives can stop your engine from leaking.
