We researched and compared the top RTV gasket makers for engine sealing, evaluating manufacturer specifications, industry standards (e.g., ASTM, SAE), and aggregated owner feedback from thousands of users. Our analysis focuses on performance, durability, value, ease of use, and safety to help you choose the right sealant for your application.
| Photo | Product | Score | Buy |
|---|---|---|---|
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Permatex Ultra Black Best Overall Sensor-safe, low odor, maximum oil resistance |
9.2 | 🛒 Check Price |
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Permatex Ultra Grey Best for High-Temp Maximum temperature resistance up to 600°F intermittent |
8.9 | 🛒 Check Price |
 |
Loctite Red RTV Best for Oil Resistance High oil resistance, sensor-safe, low volatility |
8.6 | 🛒 Check Price |
 |
Permatex Ultra Copper Best for Exhaust High temp copper silicone, resists up to 700°F |
8.3 | 🛒 Check Price |
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Versachem Ultra Grey Best Value High temp, sensor-safe, good oil resistance |
8.1 | 🛒 Check Price |
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ThreeBond 1207B Best for Japanese Engines OEM approved for many Japanese vehicles |
7.8 | 🛒 Check Price |
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CRC Industries Silicone Gasket Maker Best for Quick Repairs Fast cure, sensor-safe, multipurpose |
7.3 | 🛒 Check Price |
1. Permatex Ultra Black: Best Overall
The Permatex Ultra Black is our top pick for its proven performance in engine sealing. Based on manufacturer specs and owner feedback, it offers superior oil and coolant resistance, making it ideal for valve covers, oil pans, and timing covers. Its low odor and sensor-safe formula are added benefits for modern engines.
One real limitation: some users report that it takes longer to cure in high humidity, which can delay reassembly. If you need a fast-curing sealant for a quick repair, consider a different product. However, for most engine gasket applications, Ultra Black provides a reliable, long-lasting seal.
- Withstands extreme engine temperatures and vibration
- Excellent oil and coolant resistance
- Non-corrosive, low VOC formula
Pros: Strong, flexible bond; Works on multiple surfaces
Cons: Cure time can be longer in humid conditions
2. Permatex Ultra Grey: Best for High-Temp
The Permatex Ultra Grey is formulated for high-temperature engine parts like water pumps and thermostat housings. Our evaluation of owner reviews confirms it withstands prolonged heat without breaking down, making it a favorite for high-stress areas.
However, some users note that it is less flexible than other RTVs, which may lead to cracking under extreme vibration. If you are sealing a part that moves or flexes, consider Ultra Black instead. For static high-temp joints, Ultra Grey is an excellent choice.
- Designed for high-temp engine applications
- Resists oil, coolant, and transmission fluid
- Non-corrosive and sensor-safe
Pros: Excellent heat resistance; Good gap-filling ability
Cons: Less flexible than some silicone sealants
3. Loctite Red RTV: Best for Oil Resistance
Loctite Red RTV stands out for its exceptional oil resistance, as confirmed by owner feedback and spec sheets. It is a go-to for sealing oil pans and valve covers where oil contact is constant. Its flexibility helps accommodate minor surface imperfections.
A common complaint is that it can be messy and hard to clean up if too much is applied. This product is best for those who have experience with RTV application. Beginners might prefer a tube with a precision nozzle.
- Excellent resistance to engine oils and fuels
- Maintains flexibility under thermal cycling
- Low odor and non-corrosive
Pros: Strong bond with metal surfaces; Good for oil pan and valve cover gaskets
Cons: Can be difficult to remove if overapplied
4. Permatex Ultra Copper: Best for Exhaust
Permatex Ultra Copper is specifically designed for high-heat exhaust applications. Based on manufacturer data and user reports, it handles up to 700°F intermittent, making it ideal for exhaust manifolds, headers, and catalytic converter flanges.
However, it is not formulated for oil or coolant sealing, so avoid using it on valve covers or water pumps. If you need a multipurpose sealant, this is not the one. For exhaust work, it is a reliable choice.
- Withstands extreme exhaust heat
- Resists vibration and thermal expansion
- Non-corrosive and sensor-safe
Pros: Excellent for exhaust manifolds and headers; Good adhesion to metal
Cons: Not recommended for oil or coolant sealing
5. Versachem Ultra Grey: Best Value
Versachem Ultra Grey offers a good balance of performance and value. Our research shows it performs adequately for most engine sealing tasks, including valve covers and oil pans, at a lower price point than leading brands.
However, some users report that it may not last as long under extreme conditions. If you are building a high-performance engine or need maximum longevity, consider spending more on Permatex or Loctite. For budget-conscious DIYers, it is a solid choice.
- Cost-effective alternative to premium brands
- Good heat and oil resistance
- Works on most engine gaskets
Pros: Competitive price for the performance; Decent all-around sealant
Cons: Not as durable as top-tier options
6. ThreeBond 1207B: Best for Japanese Engines
ThreeBond 1207B is a favorite among owners of Japanese vehicles, as it is often the OEM recommended sealant. Based on owner feedback, it provides a reliable seal for timing covers and oil pans on Honda, Toyota, and Nissan engines.
One drawback is its availability; it is less common in auto parts stores and may need to be ordered online. Additionally, some users find it slightly more viscous, making application a bit trickier. If you work primarily on Japanese cars, this is worth considering.
- Specifically formulated for Japanese engines
- Excellent oil resistance
- Low odor and non-corrosive
Pros: Trusted OEM sealant for Honda, Toyota, etc.; Good adhesion to aluminum
Cons: Harder to find in retail stores
7. CRC Industries Silicone Gasket Maker: Best for Quick Repairs
CRC Silicone Gasket Maker is a good option for quick repairs or when you need to get back on the road fast. Spec sheets indicate a fast cure time, and owner reviews confirm it can be used for temporary fixes.
However, its long-term durability is not on par with top-tier RTVs. It may shrink or crack over time under high heat or pressure. This product is best for emergency situations or low-stress applications, not for critical engine seals.
- Cures quickly for fast reassembly
- Good for temporary or emergency repairs
- Works on a variety of surfaces
Pros: Fast curing time; Affordable
Cons: Not as durable as premium options
Frequently Asked Questions
What does RTV stand for and how does it work?
RTV stands for Room Temperature Vulcanizing. It is a silicone-based sealant that cures at room temperature when exposed to moisture in the air, forming a flexible, rubbery gasket that seals gaps between engine components.
How long should I wait for RTV to cure before adding fluids?
Cure time varies by product and conditions. Most RTV gasket makers recommend 1 hour for a tack-free surface and 24 hours for full cure. Check the manufacturer’s instructions. Warm, dry conditions speed up curing, while cold or humid conditions can slow it down.
Can I use RTV gasket maker on all engine parts?
RTV is suitable for many engine parts like valve covers, oil pans, and timing covers. However, avoid using it on parts that see direct fuel contact (e.g., carburetor gaskets) or high-pressure areas unless specified. Always check if the product is sensor-safe for oxygen sensors.
What is the difference between black, grey, and red RTV?
Black RTV (e.g., Permatex Ultra Black) is general-purpose with good oil resistance. Grey RTV (e.g., Ultra Grey) is for high-temperature applications. Red RTV (e.g., Loctite Red) is specialized for high oil resistance. Each has unique properties; choose based on your specific sealing needs.
How do I properly apply RTV gasket maker?
Clean and dry both surfaces thoroughly. Apply a continuous bead, typically 1/8 to 1/4 inch wide, following the part’s contour. Avoid overapplication. Assemble parts within the specified time (usually 5-10 minutes). Torque to spec and allow proper cure time before adding fluids.
Our Verdict
After researching specifications, industry standards, and owner feedback, the Permatex Ultra Black earns our top pick for its excellent all-around performance, durability, and oil resistance. For high-temperature applications, the Permatex Ultra Grey is a strong runner-up. Choose based on your specific engine sealing needs.
