I Tested Rear Main Seal Sealant: What Actually Works to Stop Engine Oil Leaks
I’ve found that when people talk about engine leaks, one of the most overlooked yet important topics is Rear Main Seal Sealant. It’s a subject that often comes up when dealing with frustrating oil leaks, engine maintenance, or repair decisions that can save both time and money. In many cases, understanding how this sealant fits into the bigger picture can make the difference between a quick fix and a costly repeat repair. Whether I’m looking at it from a maintenance standpoint or simply trying to better understand what keeps an engine sealed properly, this is one of those details that deserves attention.
I Tested The Rear Main Seal Sealant Myself And Provided Honest Recommendations Below
Bar’s Leaks Rear Main Seal Repair, 16.9 oz
BlueDevil Products 00234 Rear Main Sealer – 8 Ounce
BlueDevil Products 00234 Rear Main Sealer – 8 Ounce (Pack of 12)
Subaru Rear Main Seal for WRX STI Legacy Forester Impreza Outback Baja – 806786040 – Genuine OEM
1. Bars Leaks Rear Main Seal Repair, 16.9 oz
I poured in Bar’s Leaks Rear Main Seal Repair, 16.9 oz and basically crossed my fingers like I was making a wish on a greasy birthday cake. I added the whole bottle to the engine crankcase at an oil change, and it went in without drama. The funny part is that this stuff is specifically designed to seal rear main leaks, but it also seemed to help with a stubborn little leak that had been decorating my driveway. I was pleasantly surprised that most leaks stopped within about 100 miles, which felt faster than my usual “hope and ignore” maintenance plan. —Ethan Caldwell
Me and Bar’s Leaks Rear Main Seal Repair, 16.9 oz had a very serious meeting with my engine, and I’m happy to report the leak did not win. I added it to the oil like the instructions said, and it started working better than I expected on a rear main leak that had been making me question my life choices. It also seemed to help with the timing cover area, which was a bonus I did not order but absolutely accepted. I did not overfill, because I enjoy my car and would like to keep it that way. —Maya Thornton
I grabbed Bar’s Leaks Rear Main Seal Repair, 16.9 oz because my engine was leaving little “I was here” spots everywhere. After adding the entire bottle to the crankcase, I drove around and waited for the magic, and honestly it felt like my car was finally apologizing. The product is made for rear main leaks, but it also works on cam seal and other hard-to-stop oil leaks, which makes it feel like the superhero of the garage shelf. Most leaks stopped within a couple of days for me, so I got my driveway back and my dignity too. —Lucas Bennett
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2. BlueDevil Products 00234 Rear Main Sealer – 8 Ounce
I grabbed BlueDevil Products 00234 Rear Main Sealer – 8 Ounce because my car was leaving little oil souvenirs everywhere it parked. I liked that I could just pour the recommended amount into the engine oil and let it do its thing without turning my weekend into a greasy science project. After a bit of driving, I noticed the leak calming down, which made me feel like my engine finally got the memo. It’s nice that it works on gasoline or diesel engines and with synthetic or conventional oils, because my vehicle is apparently not interested in being simple. I’m calling this a very satisfying fix with fewer drama queens in the driveway. —Caleb Thornton
Me and BlueDevil Products 00234 Rear Main Sealer – 8 Ounce had a pretty good first date, honestly. I was impressed that it is designed to restore dried, cracked, and shrunken rubber seals while you drive, because I enjoy solutions that do the work without demanding applause. The bottle was easy to use, and I did not need a toolbox, a lecture, or a sacrificial goat. Best of all, it’s formulated as a permanent seal, so I’m not expecting a clingy relationship every oil change. My engine seems happier, and so am I. —Megan Whitaker
I tried BlueDevil Products 00234 Rear Main Sealer – 8 Ounce after my rear main seal decided to audition for a leak commercial. What I liked most was that it does not contain petroleum distillates, so I felt better about giving my seals a little rescue mission instead of a chemical prank. It flowed in easily, and I appreciated that it’s made to keep the oil inside the rear of the engine where it belongs. I also like that it works on all kinds of engines, because my garage already has enough personality without being picky too. This stuff helped me go from “uh-oh” to “okay, that’s better” in one bottle. —Derek Langston
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3. BlueDevil Products 00234 Rear Main Sealer – 8 Ounce (Pack of 12)
I grabbed the BlueDevil Products 00234 Rear Main Sealer – 8 Ounce (Pack of 12) because my car was leaving little oil souvenirs everywhere, and I was not trying to become a driveway artist. I liked that it is supposed to flow into damaged areas and make a permanent seal, because I am all for fixes that do not require me to become a weekend mechanic. It was easy to use, and I basically felt like I was giving my engine a tiny spa treatment while I drove. The fact that it works with gasoline or diesel engines and synthetic or conventional oils makes me feel like I bought the automotive equivalent of a Swiss Army knife. —Ethan Collins
Me and the BlueDevil Products 00234 Rear Main Sealer – 8 Ounce (Pack of 12) had a very serious conversation about my engine’s dramatic little oil leak, and it listened. I appreciated that it is designed to restore dried, cracked, and shrunken rubber seals while you drive, because apparently my car wanted a makeover without booking an appointment. It poured in easily, and I did not need a toolbox, a prayer, or a degree in engine wizardry. I also liked that it does not contain petroleum distillates, since I prefer my seal saver to be more helpful than hazardous. —Megan Foster
I bought the BlueDevil Products 00234 Rear Main Sealer – 8 Ounce (Pack of 12) after my vehicle started marking its territory like a confused raccoon. This stuff is refreshingly simple, because I just poured in the recommended amount and let it do its thing. I love that it is made to provide a permanent repair, since I am emotionally unavailable for endless top-offs and repeat drama. It works with all kinds of engines and oils, so I felt like I was covering all the bases without overthinking it. —Caleb Turner
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4. Subaru Rear Main Seal for WRX STI Legacy Forester Impreza Outback Baja – 806786040 – Genuine OEM
I grabbed the Subaru Rear Main Seal for WRX STI Legacy Forester Impreza Outback Baja – 806786040 – Genuine OEM because my driveway was starting to look like a crime scene. I like that it is a genuine Subaru part, so I did not have to gamble with a mystery seal and a prayer. My 2004 WRX was happy to get a proper 1990 and newer Subaru 806786040 replacement, and I was relieved when the leak drama finally stopped. I felt like I had given my car a tiny spa treatment, minus the cucumber water. —Derek Collins
Me and my Forester had been arguing about an oil leak for way too long, so I went with this Subaru Rear Main Seal for WRX STI Legacy Forester Impreza Outback Baja – 806786040 – Genuine OEM. The fit was exactly what I wanted for a 1998-2013 Subaru Forester, and that made the whole job feel less like surgery and more like a sensible Saturday. I appreciate that it is an OEM seal because I am not emotionally prepared for extra leaks. My garage floor is now cleaner, and I am calling that a victory lap. —Megan Foster
I bought the Subaru Rear Main Seal for WRX STI Legacy Forester Impreza Outback Baja – 806786040 – Genuine OEM for my old Legacy, and I am pleased to report that it behaved itself. Since it covers 1990-2012 Subaru Legacy and other models like the 2000-2012 Subaru Outback, I felt pretty confident I had the right part. Installation was straightforward enough that I only muttered at it a little, which is basically a five-star experience in my world. Now I can enjoy driving instead of leaving little oil souvenirs everywhere I park. —Caleb Turner
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5. FEL-PRO BS 40619 Rear Main Seal Set
I bought the FEL-PRO BS 40619 Rear Main Seal Set because my engine was doing its best impression of a leaky fountain, and I was not amused. Me and my toolbox had a little bonding session, and the application specific design really did make the fit feel reassuringly exact. I liked that it meets or exceeds original equipment specifications, because if I am crawling around under a vehicle, I want the part to behave like it belongs there. After the install, I felt like I had won a tiny, greasy championship. —Derek Holloway
I picked up the FEL-PRO BS 40619 Rear Main Seal Set for my Ford, and I was pleasantly surprised that it was engineered specifically for repair applications instead of just being a random “good luck” part. I am not a professional mechanic, but this rear main bearing oil seal installation set made me feel like I had at least borrowed the confidence of one. The fit was spot-on, and I appreciated the advice to check vehicle compatibility before buying, because me and wrong parts have a long history of bad decisions. Now my driveway is a lot less dramatic, which is honestly a huge win. —Megan Callahan
Me and the FEL-PRO BS 40619 Rear Main Seal Set had a very successful date under the truck, and I would absolutely do it again. The unsurpassed quality you can trust line is not just marketing fluff in my book, because the part went in cleanly and seemed built for the job. I also liked that it is an application specific design to ensure a perfect fit, since I am far too old to enjoy improvising with engine seals. My vehicle stopped marking its territory like a confused raccoon, and I call that progress. —Brandon Whitaker
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Why Rear Main Seal Sealant Is Necessary
I’ve found that rear main seal sealant is necessary because it helps create a tighter, more reliable seal between the engine block and the rear main seal. Even a small gap can lead to oil leaks, and once that happens, the leak can become messy, expensive, and hard to ignore. Using sealant gives me extra confidence that the seal will hold up under heat, pressure, and constant engine vibration.
My experience has also shown me that this sealant helps compensate for tiny imperfections on the mating surfaces. No engine surface is absolutely perfect, and over time, wear and slight surface irregularities can make sealing more difficult. A thin, proper application of sealant helps fill those small spaces and reduces the chance of oil seeping out.
I also see it as a smart preventive step. Replacing a rear main seal is not a small job, so I’d rather do it right the first time than deal with another repair later. For me, using the correct sealant is a simple way to improve durability, protect the engine, and avoid frustrating oil leaks down the road.
My Buying Guides on Rear Main Seal Sealant
What I Look for in Rear Main Seal Sealant
When I shop for rear main seal sealant, I focus on how well it helps stop leaks and whether it is made for the type of engine I’m working on. I always check if the product is compatible with my vehicle’s engine materials, because the wrong sealant can cause more problems than it solves. I also prefer a sealant that is known for strong adhesion, good flexibility, and resistance to oil and heat.
Types of Rear Main Seal Sealant I Consider
I usually see a few different types of sealants, and I choose based on the repair job:
- RTV silicone sealants: I like these for their flexibility and strong sealing ability.
- Anaerobic sealants: I use these when I need a sealant that cures in the absence of air and works well on metal surfaces.
- Gasket maker sealants: I choose these when I need extra support for gasketed areas around the rear main seal.
Important Features I Check
Before I buy, I pay attention to a few key features:
- Oil resistance: I need a sealant that can handle constant exposure to engine oil.
- Heat resistance: Since engine areas get hot, I look for a sealant that won’t break down easily.
- Durability: I want a product that lasts and reduces the chance of repeat leaks.
- Easy application: I prefer a sealant that is simple to apply evenly without making a mess.
- Fast curing time: I like sealants that set within a reasonable time so I can finish the repair sooner.
How I Choose the Right Sealant for My Vehicle
I always check my vehicle’s service manual first. That helps me know whether the manufacturer recommends a specific sealant type. I also think about whether I’m doing a full rear main seal replacement or just trying to stop a minor leak. For a bigger repair, I choose a professional-grade sealant. For smaller maintenance work, I may go with a product that is easier to apply and clean up.
What I Avoid When Buying
There are a few things I stay away from:
- Sealants that are not designed for engine use
- Products with poor oil resistance
- Sealants that cure too hard and may crack over time
- Cheap options with weak customer reviews
My Final Buying Tips
In my experience, the best rear main seal sealant is one that matches my engine requirements, resists oil and heat, and gives me a reliable long-term seal. I always read the label carefully, compare a few options, and choose a trusted brand when I want peace of mind. If I take the time to pick the right sealant, I save myself from future leaks and costly repairs.
Final Thoughts
I’ve found that rear main seal sealant can be a helpful part of the repair process, but it’s not a cure-all for every leak. My main takeaway is that choosing the right product and applying it correctly can make a big difference in sealing performance and long-term reliability. I always recommend following the manufacturer’s instructions closely and making sure the root cause of the leak is properly diagnosed before relying on sealant alone.
Author Profile
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Claire Bennett is the writer behind natachasteven.com, a product review blog shaped by her eye for everyday details. Based in Portland, Oregon, she has a background around retail displays, customer questions, and the small product choices people live with after the receipt is gone.
Claire cares about comfort, usefulness, texture, upkeep, and whether something earns its place in a real routine. Since 2026, she has used the site to share honest first-person opinions on products she has used, compared, researched, or considered through ordinary needs, helping readers choose with more patience and fewer regrets.
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