Best Engine Sealants

Looking for the best engine sealants to keep your vehicle in top shape? We’ve tested and reviewed the top 10 options to help you find the perfect one for your needs.

Engine sealants are essential for keeping your vehicle running smoothly. They prevent leaks and protect vital parts from damage. Choosing the right one can save you time and money.

We’ve tested and reviewed the best engine sealants to help you make an informed decision. Whether you’re fixing a coolant leak or sealing an oil pan, we’ve got you covered.

List of Top 10 Engine Sealants

Title	Best For	Price
ACDelco GM Original Equipment 10-2006 (88864346) RTV Engine Sealant – 75 g	This ACDelco RTV Engine Sealant is perfect for anyone working on car engines. It’s great for sealing oil pans, covers, and joints quickly and easily.	View on Amazon (paid link)
ACDelco GM Original Equipment 10-2010 (12378521) RTV Engine Sealant – 5.3 oz Cartridge	This ACDelco RTV Engine Sealant is perfect for anyone working on car engines. Whether you’re fixing an oil pan, manifold, or cam cover, this sealant is easy to use and works fast.	View on Amazon (paid link)
K-Seal ST5501 Multi-Purpose One Step Permanent Coolant Leak Repair, 8oz, Pour and Go, Mixes with All Antifreeze, No Flushing Required	K-Seal ST5501 is perfect for anyone with a leaky engine. It’s easy to use and works fast, saving you time and money.	View on Amazon (paid link)
RTV Silicone Gasket Maker, High Temp Silicone Resist Oil, Anti-Freeze RTV Silicone Sealant for Engines, Gearboxes, Pumps, Superchargers (Black, 170g)	This RTV Silicone Gasket Maker is perfect for car owners, mechanics, and DIY enthusiasts who want to stop leaks and keep engines running smoothly. It’s great for fixing gearboxes, pumps, and superchargers too.	View on Amazon (paid link)
Bar’s Leaks 1109 Liquid Copper Block Seal, Intake and Radiator Stop Leak, 18 oz. \| One Step, Safe for All Cooling Systems	This product is perfect for anyone with a vehicle that has a cooling system leak. It’s easy to use and works for cars, trucks, vans, SUVs, and RVs.	View on Amazon (paid link)
RTV Silicone Gasket Maker, High Temp Silicone Resist Oil, Anti-Freeze RTV Silicone Sealant for Engines, Gearboxes, Pumps, Superchargers (Red, 170g)	This RTV Silicone Gasket Maker is perfect for car owners, mechanics, and DIY enthusiasts who want to stop leaks and keep engines, gearboxes, and pumps running smoothly. It’s easy to use and works great under high heat, cold, and pressure.	View on Amazon (paid link)
Permatex 80632 Thread Sealant with PTFE, 4 oz., Cream	This Permatex 80632 Thread Sealant is perfect for anyone working on air, oil, diesel fuel, or hydraulic systems. It’s ideal for sealing fittings in air conditioning, temperature sending, and hydraulic setups.	View on Amazon (paid link)
LOCBONDSO Black RTV Silicone Sealant, Silicone Gasket Maker, High Temp Up to 600F, Sensor Safe, Oil Resistance Flexible for Automotive, Engine, Gearboxes, 3 oz	This black RTV silicone sealant is perfect for car lovers and DIY enthusiasts. It’s great for fixing engines, gearboxes, and more.	View on Amazon (paid link)
Permatex 80019 Aviation Form-A-Gasket No. 3 Sealant, 4 oz.	Permatex 80019 Aviation Form-A-Gasket No. 3 Sealant is perfect for anyone working on engines or machinery. Whether you’re fixing cars, planes, or other vehicles, this sealant is ideal for sealing hoses and gaskets. It works well in extreme temperatures and resists oil, grease, and gasoline.	View on Amazon (paid link)
POLIXEL Red High Temperature RTV Silicone Gasket Maker – Oil Resistant Sealant for Engines, Exhaust Manifolds, Oil Pans, Gearboxes, Pumps, Superchargers & Automotive Parts – 3.4 oz	POLIXEL Red High Temperature RTV Silicone Gasket Maker is perfect for DIY enthusiasts, mechanics, and homeowners who need a reliable, high-temp sealant for automotive and household projects.	View on Amazon (paid link)

Detailed Reviews

Discover the top 10 engine sealants handpicked for performance and value. Each product is expert-reviewed and backed by customer feedback, ensuring you find the perfect match for your needs. Whether you’re tackling leaks, repairs, or maintenance, this guide makes choosing easy and reliable.

1. ACDelco GM Original Equipment 10-2006 (88864346) RTV Engine Sealant – 75 g

ACDelco GM Original Equipment RTV Engine Sealant is a high-quality product designed for engine components. It works well on oil pans, covers, and joints, making it a versatile solution for your engine needs.

This sealant is easy to apply and cures quickly when exposed to air. You can fill with oil or coolant right after use. Made in the USA, it’s a reliable choice for your vehicle.

Pros	Cons
Versatile use on multiple engine parts. Quick application, immediate assembly after use. High viscosity, cures fast when exposed to air. Made in the USA, reliable quality.	Not for all engine parts, check compatibility first. Cures quickly, no room for mistakes during application. High viscosity may require extra effort to spread evenly.

Perfect For:

This ACDelco RTV Engine Sealant is perfect for anyone working on car engines. It’s great for sealing oil pans, covers, and joints quickly and easily.

Ready to Purchase?

View Price on Amazon (paid link)

2. ACDelco GM Original Equipment 10-2010 (12378521) RTV Engine Sealant – 5.3 oz Cartridge

ACDelco GM Original Equipment 10-2010 is a high-quality RTV engine sealant. It comes in a 5.3 oz cartridge. This product is designed for engine components.

It works on oil pans, ladder frames, and manifold corners. You can also use it on intake, manifold end seals, and cam covers. The sealant cures when exposed to air.

This engine sealant is easy to apply. It allows for quick assembly. You can fill with oil or coolant right after use.

Pros	Cons
Versatile use on multiple engine parts. Quick application, immediate assembly possible. High viscosity ensures strong, reliable seals. Cures fast when exposed to air.	Not for all materials, may not bond well with plastics. Air curing limits use in enclosed or deep-seated areas. High viscosity can make precise application tricky.

Perfect For:

This ACDelco RTV Engine Sealant is perfect for anyone working on car engines. Whether you’re fixing an oil pan, manifold, or cam cover, this sealant is easy to use and works fast.

Ready to Purchase?

View Price on Amazon (paid link)

3. K-Seal ST5501 Multi-Purpose One Step Permanent Coolant Leak Repair, 8oz, Pour and Go, Mixes with All Antifreeze, No Flushing Required

K-Seal ST5501 is a fast, permanent fix for coolant leaks. It works in minutes to seal leaks in your engine. Just shake, pour, and go—no draining or flushing needed.

It stops holes and cracks in your radiator, head gasket, and more. The unique formula works with all antifreeze types. It’s safe and efficient for your engine.

Trusted by mechanics worldwide, K-Seal is professional-grade. It’s cost-effective and lasts the lifetime of your engine. Millions use it for reliable repairs.

Pros	Cons
Fixes leaks fast, saving time and money on repairs. One-step solution—shake, pour, and go, no hassle. Works with all antifreeze, fits any vehicle type. Trusted by pros, proven to last for engine life.	Not for oil leaks, only fixes coolant system issues. May not work on large or severe leaks in engines. No instant fix, requires engine running for best results.

Perfect For:

K-Seal ST5501 is perfect for anyone with a leaky engine. It’s easy to use and works fast, saving you time and money.

Ready to Purchase?

View Price on Amazon (paid link)

4. RTV Silicone Gasket Maker, High Temp Silicone Resist Oil, Anti-Freeze RTV Silicone Sealant for Engines, Gearboxes, Pumps, Superchargers (Black, 170g)

RTV Silicone Gasket Maker, High Temp Silicone Resist Oil, Anti-Freeze RTV Silicone Sealant for Engines, Gearboxes, Pumps, Superchargers (Black, 170g)

RTV Silicone Gasket Maker is a high-temp sealant made for automotive engines. It stops oil and gas leaks and keeps engines running smoothly. Use it for gearboxes, pumps, and superchargers too.

It cures fast into a leak-proof gasket, replacing the need for cut gaskets. It stays flexible and won’t shrink or crack under heat, cold, or pressure.

This oil-resistant sealant is waterproof and freeze-proof. It fills gaps completely and prevents fluid leaks. Always test seals before use for best results.

Pros	Cons
Stops leaks in engines, gearboxes, and pumps. Resists heat, cold, oil, and pressure for strong seals. Cures fast into a flexible, crack-proof gasket. Easy to use for quick, reliable repairs.	Curing time varies, needing careful monitoring for best results. Pressure required during curing, adding an extra step to apply. Sealing test mandatory, ensuring safety but adding time to the process.

Perfect For:

This RTV Silicone Gasket Maker is perfect for car owners, mechanics, and DIY enthusiasts who want to stop leaks and keep engines running smoothly. It’s great for fixing gearboxes, pumps, and superchargers too.

Ready to Purchase?

View Price on Amazon (paid link)

5. Bar’s Leaks 1109 Liquid Copper Block Seal, Intake and Radiator Stop Leak, 18 oz. | One Step, Safe for All Cooling Systems

Bar’s Leaks 1109 Liquid Copper Block Seal stops cooling system leaks fast. It works in one easy step—just pour it into your radiator. This safe formula works with all types of coolant and won’t harm your system.

It fixes leaks permanently in plastic, aluminum, and cast iron parts. No draining is needed, and it’s compatible with antifreeze.

Pros	Cons
Permanently fixes cooling system leaks in one easy step. Safe for all cooling systems, no draining needed. Works with any antifreeze type, hassle-free. Fiber additives strengthen seals for lasting repair.	Not for oil leaks or transmission issues, only cooling systems. May clog small passages if overused or misapplied. Temporary fix for severe leaks, professional repair still needed.

Perfect For:

This product is perfect for anyone with a vehicle that has a cooling system leak. It’s easy to use and works for cars, trucks, vans, SUVs, and RVs.

Ready to Purchase?

View Price on Amazon (paid link)

6. RTV Silicone Gasket Maker, High Temp Silicone Resist Oil, Anti-Freeze RTV Silicone Sealant for Engines, Gearboxes, Pumps, Superchargers (Red, 170g)

RTV Silicone Gasket Maker is a high-temp sealant made for automotive engines. It stops oil and gas leaks and keeps your engine running smoothly.

It works fast, cures into a strong gasket, and stays flexible under pressure. No shrinking, no cracking, just a reliable seal.

Use it on engines, gearboxes, pumps, and more. It’s oil-resistant, waterproof, and freeze-proof, ensuring long-lasting protection.

Pros	Cons
Stops leaks fast, keeps engines running smoothly. Flexible and strong, resists heat, cold, and pressure. Oil-resistant, waterproof, and freeze-proof for all conditions. Quick cure, saves time and ensures reliable seals.	Not for all materials, may damage some surfaces. Requires pressure during curing, extra effort needed. Test needed after sealing, adds extra step.

Perfect For:

This RTV Silicone Gasket Maker is perfect for car owners, mechanics, and DIY enthusiasts who want to stop leaks and keep engines, gearboxes, and pumps running smoothly. It’s easy to use and works great under high heat, cold, and pressure.

Ready to Purchase?

View Price on Amazon (paid link)

7. Permatex 80632 Thread Sealant with PTFE, 4 oz., Cream

Permatex 80632 is a reliable thread sealant with PTFE. It comes in a 4 oz. cream tube. This product is easy to use and highly effective.

It outperforms tapes and pipe dopes, making it a top choice for sealing. The sealant resists pressure in air, oil, diesel fuel, and hydraulic systems.

Use it for air conditioning fittings, temperature sending fittings, and hydraulic fittings. It remains pliable in higher and lower temperatures, ensuring a lasting seal.

Pros	Cons
Seals better than tapes and pipe dopes for reliable connections. Works in all weather, staying flexible in hot or cold temps. Handles air, oil, diesel, and hydraulic systems with ease. Great for AC, temperature, and hydraulic fittings – versatile use.	Not for gasoline or oxygen systems. May require extra care to avoid messy application. Cream color may show on some surfaces.

Perfect For:

This Permatex 80632 Thread Sealant is perfect for anyone working on air, oil, diesel fuel, or hydraulic systems. It’s ideal for sealing fittings in air conditioning, temperature sending, and hydraulic setups.

Ready to Purchase?

View Price on Amazon (paid link)

8. LOCBONDSO Black RTV Silicone Sealant, Silicone Gasket Maker, High Temp Up to 600F, Sensor Safe, Oil Resistance Flexible for Automotive, Engine, Gearboxes, 3 oz

LOCBONDSO Black RTV Silicone Sealant, Silicone Gasket Maker, High Temp Up to 600F, Sensor Safe, Oil Resistance Flexible for Automotive, Engine, Gearboxes, 3 oz

LOCBONDSO Black RTV Silicone Sealant is oil-resistant and sensor-safe, perfect for automotive and engine repairs. It withstands extreme temperatures, from -76°F to 600°F, ensuring a durable seal. The flexible formula cures into a strong elastomer, ideal for gasket replacements.

This 3 oz tube is easy to apply and stores conveniently. It dries in 1 hour and fully cures in 18-24 hours, making it reliable for various applications.

Pros	Cons
Oil-resistant and sensor-safe for reliable seals. Withstands extreme temps from -76°F to 600°F. Flexible and durable for any shape or use. Easy to apply, quick to dry, long-lasting.	Long curing time: Takes 18-24 hours to fully cure. Small quantity: Only 3 oz per tube, may not last long. Not instant use: Requires 1 hour to dry before handling.

Perfect For:

This black RTV silicone sealant is perfect for car lovers and DIY enthusiasts. It’s great for fixing engines, gearboxes, and more.

Ready to Purchase?

View Price on Amazon (paid link)

9. Permatex 80019 Aviation Form-A-Gasket No. 3 Sealant, 4 oz.

Permatex 80019 is a slow-drying, non-hardening sealant perfect for machined surfaces. It resists gasoline, oil, and grease, making it tough and reliable. Use it for sealing hoses or creating solid gaskets with ease.

This sealant works in extreme temperatures, from -65°F to 400°F. It’s approved for aviation and automotive use, so it’s versatile and dependable.

Pros	Cons
Slow-drying formula for easy application and perfect sealing. Resists gasoline, oil, and grease for long-lasting performance. Approved for aviation and automotive use, versatile and reliable. Works in extreme temperatures from -65°F to 400°F.	Slow-drying formula may delay project completion. Not ideal for fast-paced repairs or quick fixes. Brush-top application can be messy for precise work.

Perfect For:

Permatex 80019 Aviation Form-A-Gasket No. 3 Sealant is perfect for anyone working on engines or machinery. Whether you’re fixing cars, planes, or other vehicles, this sealant is ideal for sealing hoses and gaskets. It works well in extreme temperatures and resists oil, grease, and gasoline.

Ready to Purchase?

View Price on Amazon (paid link)

10. POLIXEL Red High Temperature RTV Silicone Gasket Maker – Oil Resistant Sealant for Engines, Exhaust Manifolds, Oil Pans, Gearboxes, Pumps, Superchargers & Automotive Parts – 3.4 oz

POLIXEL Red High Temperature RTV Silicone Gasket Maker - Oil Resistant Sealant for Engines, Exhaust Manifolds, Oil Pans, Gearboxes, Pumps, Superchargers & Automotive Parts - 3.4 oz

POLIXEL Red High Temperature RTV Silicone Gasket Maker is a powerful sealant for extreme conditions. It withstands high heat and resists oil, making it perfect for engines and automotive parts.

This easy-to-use sealant cures quickly and bonds strongly. It’s flexible, durable, and versatile for multiple projects.

Pros	Cons
Withstands 650°F heat and oil for extreme engine seals. Flexible, durable seal prevents leaks and cracks over time. Ready-to-use tube applies smoothly, cures in 24 hours. Versatile for automotive and household repairs in one tube.	Not for food use: Avoid contact with food or cooking utensils. Strong smell: Ventilate well when applying to avoid fumes. Long cure time: Takes 24 hours to fully set and cure.

Perfect For:

POLIXEL Red High Temperature RTV Silicone Gasket Maker is perfect for DIY enthusiasts, mechanics, and homeowners who need a reliable, high-temp sealant for automotive and household projects.

Ready to Purchase?

View Price on Amazon (paid link)

Buying Guide

Engine sealants keep your vehicle running smoothly by preventing leaks and protecting vital parts. Choosing the right one can save you time and money.

Buying the Best Engine Sealant: A Pro Guide
Finding the perfect engine sealant doesn’t have to be hard. We’ve tested top products to help you make a smart choice. Here’s what to consider:

Type of Leak:
Know where the leak is. Some sealants work best for coolant leaks, while others are great for oil pans or gaskets.
Temperature Resistance:
Engines get hot! Choose a sealant that can handle high temperatures without breaking down.
Compatibility:
Make sure the sealant works with your engine’s materials, like plastic, aluminum, or cast iron.
Ease of Use:
Look for sealants that are easy to apply and cure quickly. Some even let you fill with oil or coolant right after use.
Durability:
Pick a sealant that lasts long and resists oil, water, and pressure. You want a reliable seal that won’t fail.
Versatility:
Some sealants work for engines, gearboxes, and pumps. A multi-purpose option can save you money.
Safety:
Ensure the sealant is safe for your engine and won’t cause damage. Sensor-safe options are a plus.

With these tips, you’ll find the best engine sealant for your needs. Keep your vehicle running smoothly and avoid costly repairs!