5 Best Rear Main Seal Leaks Fixes to Keep Your Engine Running Smoothly

If you've ever faced the frustration of dealing with a rear main seal leak in your vehicle, you know how essential it is to address it promptly.

The market offers various solutions to tackle this issue, from trusted products like Bars Leaks Rear Main Seal Repair to innovative options like BlueDevil Products 00234 Rear Main Sealer.

However, how do you determine the most effective fix for your specific situation? Understanding the factors that influence your choice can make a significant difference in resolving this common engine problem seamlessly.

Bars Leaks Rear Main Seal Repair, 16.9 oz

For those seeking a quick and effective solution to seal rear main leaks in their engine, Bars Leaks Rear Main Seal Repair, 16.9 oz is the ideal choice. This product is designed to seal rear main leaks, timing cover leaks, cam seal leaks, and other challenging oil leaks.

Simply add it to your engine oil, and most leaks will stop within 100 miles or 2 days of driving. Bars Leaks Rear Main Seal Repair restores seals quickly and safely, providing an affordable and efficient solution. It works with all gasoline and diesel engines, containing additives that effectively stop leaks in severely worn seals and crankshafts.

With easy application and proven effectiveness, Bars Leaks Rear Main Seal Repair is a reliable option to keep your engine running smoothly.

Best For: Individuals looking for a quick and affordable solution to seal rear main leaks in their engine.


  • Easy to use
  • Works with ALL gasoline and diesel engines
  • Restores seals quickly and safely


  • Mixed reviews on effectiveness

BlueDevil Products 00234 Rear Main Sealer – 8 Ounce

To achieve smoother engine performance and resolve rear main seal leaks effectively, consider BlueDevil Products 00234 Rear Main Sealer – 8 Ounce. This product is designed to fix leaks in the rear main seal of your engine, providing a permanent seal by flowing into damaged areas.

You can easily pour the recommended amount into your engine oil, and it works as a permanent repair that doesn't require additional applications during oil changes. BlueDevil Rear Main Sealer restores dried, cracked, and shrunken rubber seals to their original condition while you drive, and it's safe to use as it doesn't contain petroleum distillates that could harm seals.

Compatible with gasoline or diesel engines using synthetic or conventional oils, this compact and easy-to-use sealer has received positive reviews for successfully addressing rear main seal leaks in various vehicles.

Best For: Those looking for a permanent solution to rear main seal leaks in their engine.


  • Provides a permanent seal by flowing into damaged areas of the rear main seal.
  • Restores dried, cracked, and shrunken rubber seals to their original condition.
  • Compatible with gasoline or diesel engines using synthetic or conventional oils.


  • Mixed reviews on effectiveness, with some users needing additional repairs.

STP High Mileage Oil Treatment + Stop Leak – 15 FL OZ

Reduce engine leaks and improve performance with STP High Mileage Oil Treatment + Stop Leak – 15 FL OZ, designed for vehicles with over 75,000 miles. This 15 fl oz bottle contains a high-viscosity formula with ZDDP oil additive specifically tailored for high-mileage vehicles.

Not only does it reduce friction between engine parts, but it also acts as a leak stopper, preventing engine leaks, noises, and smoking. Customers have given positive feedback on its ability to decrease oil consumption and prevent leaks. While some caution about potential adverse effects on older vehicles exists, overall satisfaction with the product's performance is prevalent.

For optimal results, consider driving a certain distance after application to observe the reduction in leaks.

K-Seal ST5501 Multi Purpose One Step Permanent Coolant Leak Repair

If you're dealing with coolant leaks in your vehicle's engine, the K-Seal ST5501 Multi Purpose One Step Permanent Coolant Leak Repair offers a simple and effective solution. This product, which comes in an 8 fluid ounce bottle, is designed to mix with all antifreeze and can fix cracks and leaks in various engine components such as the radiator, head gasket, freeze plugs, cylinder heads, heater core, water pump casing, and engine blocks. Users have reported positive experiences, with one individual mentioning improved engine performance and no leaks even after driving over 20,000 miles post-application. While some users faced overheating issues that required a system flush, many recommend this product as a cost-effective alternative to expensive engine replacements.

Best For: Those looking for a cost-effective solution to fix coolant leaks in various engine components without the need for expensive engine replacements.


  • Easy application process without the need to drain coolant
  • Effective in fixing cracks and leaks in multiple engine parts
  • Compatible with all types of antifreeze


  • Potential risk of clogging leading to overheating issues

ATP Automotive AT-205 Re-Seal Stops Leaks, 8 Ounce Bottle

For those seeking a fast and effective solution to address leaks in various vehicle systems, the ATP Automotive AT-205 Re-Seal offers a professional strength resealer that rejuvenates rubber seals and gaskets, promoting smoother engine performance. This fast-acting resealer is compatible with conventional and synthetic oils, ATF, gear oil, power steering fluids, and hydraulic oil. It doesn't contain petroleum distillates and won't over-swell or breakdown seals, making it safe for internal bearings and components. An 8oz bottle can treat a 6-quart capacity, providing a convenient solution for leak issues. Users have reported successful results in stopping leaks in power steering pumps, hydraulic systems, snow plows, and engine components, making ATP-205 a reliable choice for addressing small leaks effectively.

Best For: Individuals looking to quickly and effectively address small leaks in various vehicle systems without causing seal damage.


  • Fast-acting resealer for quick leak stoppage
  • Compatible with a wide range of fluids for versatile use
  • Safe for internal bearings and components


  • Caution needed for potential effects on oil pressure

Factors to Consider When Choosing Rear Main Seal Leaks

When selecting rear main seal leaks fixes, you should consider important features, compatibility with your engine, and application instructions.

It's crucial to have clear effectiveness expectations and to follow user safety precautions for optimal results.

Make informed choices based on these factors to ensure smooth engine performance.

Important Features

Consider the compatibility of the rear main seal repair product with your vehicle's engine type and oil type when selecting a solution for addressing leaks.

Opt for products that offer a permanent seal rather than temporary fixes to ensure long-lasting results.

Prioritize products that are safe to use and don't contain harmful additives that could potentially damage the seals further.

Evaluate the ease of application of the product, including the application process and any specific instructions provided.

Additionally, reading user reviews can provide valuable insights into the effectiveness of the product in addressing rear main seal leaks, offering real customer experiences to guide your decision-making process.

Make sure to consider these important features when choosing the right solution for your vehicle.

Compatibility Considerations

To ensure a successful repair for rear main seal leaks, prioritize verifying the compatibility of the product with your vehicle's engine type and oil specifications. Check if the product is suitable for gasoline or diesel engines and safe for use with both synthetic and conventional oils.

It's essential to confirm compatibility with high-mileage vehicles, particularly those with over 75,000 miles. Consider whether the product is designed to work across various engine types to effectively address rear main seal leaks. Look for products that are safe for internal engine components and don't contain harmful petroleum distillates.

Application Instructions

For successful application of rear main seal repair products, carefully adhere to the manufacturer's instructions to ensure proper sealing of the engine. Make sure the engine is at the recommended temperature before adding the sealant to the crankcase.

Avoid overfilling the engine with the sealant, as this can cause potential issues. Allow the recommended time or mileage for the sealant to circulate and take effect before evaluating the results.

If unsure about the application process, consider seeking guidance from a professional mechanic. Following these steps diligently will help maximize the effectiveness of the rear main seal repair product and keep your engine running smoothly.

Effectiveness Expectations

When selecting a rear main seal leak product, evaluating the severity of the leak and the condition of the seal becomes key to determining its effectiveness. Understanding the limitations of these products is crucial for managing expectations regarding leak prevention.

Factors such as the age and mileage of the vehicle play a significant role in assessing the potential effectiveness of rear main seal leak solutions. Proper application, following manufacturer guidelines, and regular maintenance are also essential considerations that can impact the overall effectiveness of these repair products.

Having realistic expectations about the outcomes of using rear main seal repair products is important to avoid disappointment and ensure informed decision-making.

User Safety Precautions

Consider safety precautions when choosing rear main seal leak products to protect yourself during the repair process.

Always start by ensuring the engine is cool to prevent burns. Wear protective gear like gloves and safety glasses when handling chemicals or engine parts. Carefully follow the manufacturer's instructions to avoid engine damage and additional leaks.

Be aware of any specific precautions for the product, such as skin or eye contact warnings. If you feel uncertain about the repair process, it's wise to seek professional help to ensure safety and effectiveness.

Prioritizing these safety measures will help you complete the repair smoothly and without harm.

Maintenance Recommendations

To ensure the smooth operation of your vehicle, prioritize regular inspection and maintenance of the rear main seal to detect and address leaks promptly. Use high-quality engine oil and adhere to manufacturer recommendations for oil changes. Watch out for signs of rear main seal leaks, such as oil puddles under the car or a decrease in oil levels.

Act swiftly to fix any leaks to prevent potential engine damage. Incorporate sealants or additives specifically formulated to halt rear main seal leaks into your maintenance routine. By staying proactive and attending to leaks early, you can maintain your engine's performance and longevity.

Warranty Information

Considering various factors when selecting a rear main seal leaks product, the warranty information plays a crucial role in determining the level of protection and support available for your purchase.

Warranty details can vary among manufacturers, with some products offering satisfaction guarantees or return policies for added reassurance. It's essential to understand the coverage provided by the warranty, including duration, conditions, and any limitations, before making a decision.

The terms of the warranty can significantly impact the overall value and reliability of the rear main seal repair product. By reviewing and comparing warranty information, you can make an informed choice that not only addresses your current needs but also offers peace of mind for the future.

Frequently Asked Questions

Can I Use These Products in a Manual Transmission Vehicle?

Yes, you can use these products in a manual transmission vehicle. They are designed to work effectively across different types of vehicles, ensuring proper sealing and maintenance for your transmission system.

Are These Products Safe to Use With Synthetic Oil?

Yes, these products are safe to use with synthetic oil. They are designed to work effectively with various types of oils, including synthetic blends. You can confidently use them in your vehicle without any concerns.

How Long Do These Products Typically Last Before Needing Reapplication?

Typically, these products can last for several thousand miles before requiring reapplication. Keep an eye on your engine's performance and oil levels to gauge when it's time for another treatment to maintain optimal functioning.

Will Using These Products Void My Vehicle's Warranty?

Using these products generally won't void your vehicle's warranty. However, it's essential to verify with your manufacturer or dealership. Maintenance with approved products can often help maintain your warranty coverage while keeping your engine running smoothly.

Can These Products Fix Rear Main Seal Leaks in Older Vehicles With High Mileage?

Yes, these products can help fix rear main seal leaks in older vehicles with high mileage. They are designed to provide a temporary solution by rejuvenating the seal, but for a long-term fix, a professional inspection may be needed.


In conclusion, addressing rear main seal leaks promptly is crucial to maintaining a healthy engine. By using one of the recommended products like Bars Leaks, BlueDevil, STP, K-Seal, or ATP Automotive, you can effectively repair leaks and prevent further damage.

Remember to consider factors such as compatibility with your vehicle and ease of application when choosing a solution. Keep your engine running smoothly with these top fixes for rear main seal leaks.