When buying gasket maker at my local auto-supplies store some time back, I was unsure about whether or not the color of the tube made any difference. The only thing I could see was a different temperature rating on the tube itself.

At the time I chose black because it had a higher temperature rating than red, but was concerned because the relevant forum was suggesting to use grey RTV for timing cover reassembly.


  • What do the different colors signify?
  • Are there other colors that I am not aware of?
  • Is operating temperature the only differentiating factor? What about properties like cure time and water/oil resistance?
  • Are there automotive applications where I should use only one type of RTV and not others?
  • Could you edit this to explain what the acronym RTV stands for? (Room Temperature Vulcanisation)
    – Nick C
    Commented Jul 13, 2015 at 11:00

6 Answers 6


Since every manufacturer can use whatever color they want to create their flavor of gasket material. RTV or Room Temperature Vulcanization sealants come in many types, colors, flavors, and work to seal for many different occasions. Also remember that each manufacturer may utilize the same color for different means. Black sealant is very commonly used in the manufacture of sealants. This just adds more to the confusion.

Not that I have empirical evidence of such, but I believe Permatex is most likely the preeminent maker of RTV gasket maker. They have a whole list of other products as well, but the sealants they make do work pretty well. I'll use their colors scheme to describe the differences and when they should be used. Ultimately, though, it comes down to reading the package as to if the product you are looking at is right for your needs.

Permatex has several different types of sealants. Most of which are RTV, but some specify use in anaerobic situations where there isn't any air to do the curing. I will try to break out the different types of sealants and how they are utilized:

  • Anaerobic (color unknown) - Used where no air will be present after being applied. This product would probably work well for under water situations, such as boat jet drive, or as a temporary fix to replace an o-ring.

  • Gasket Makers

    • The Right Stuff (Black) - This product is for general use and can be utilized almost anywhere and in any kind of situation. It boasts a quick turnaround so you can get your equipment back into service quickly. Many OEM manufacturers use this product on their assembly lines. It is good from -75°F to 450°F (-59°C to 232°C) continuous, 500°F (260°C) intermittent; resists ATF, coolant, oil and other shop fluids, and is sensor-safe.
    • The Right Stuff 1-Minute (Grey) - Specifically designed for high torque situations. Permatex boasts a "torque and go" attitude with this product. This product is specified by many non-US manufacturers. It is good up to 450°F (232°C) continuous; 500°F (260°C) intermittent.
    • The Right Stuff (Grey) - Basically the same as the 1-minute type. It just takes a little longer to cure and go back into service.
    • Ultra Black Maximum Oil Resistance (Black)) - Used in areas where oil resistance is a must. This would be oil pans or valve cover gaskets. Temperature range -65°F to 500°F (-54°C to 260°C) intermittent.
    • Ultra Copper Maximum Temperature (Copper) - As the name implies, to be used where high temps are present. I've used this stuff on my header gaskets at the collector with good results. It helps seal the gasket and helps it last longer as well. This product is good up to 700°F intermittent. It works to seal liquids as well.
    • Ultra Grey Rigid High-Torque (Grey) - Eight times more flexible than cork/composite gaskets; three times more oil resistant than conventional silicones. Temperature range -65°F to 500°F (-54°C to 260°C) intermittent. Used where you'd expect to need more flexibility than normal.
    • Ultra Blue Multipurpose (Blue) - As the name implies, this is an all purpose gasket material. Temperature range -65°F to 500°F (-54°C to 260°C) intermittent. OEM specified for a lot of different applications.
    • Sensor-Safe Blue (Blue) - General use RTV. Will not foul O2 sensors. ature range -65°F to 500°F (-54°C to 260°C) intermittent.
    • High-Temp Red (Red) - Universal, but can be used in hi-temp situations. Not as high temp as Ultra Copper. Temperature range -65°F to 650°F (-54°C to 343°C) intermittent.
    • Sensor-Safe High-Temp (Color unknown - Assume black) - Same as the High-Temp Red, but is won't foul O2 sensors.
    • Water Pump & Thermostat (Color unknown - Assume black) - Specified where high concentrations of water and glycol are present.
    • Automatic Transmission (Color unknown - Assume black) - Specified for automatic transmission pan gaskets. Resists tranny fluids.
    • Gear Oil (Color unknown - Assume black) - Used on differential housings to seal in gear oil.
  • Gasket Sealers

This list is not exhaustive. As you can tell, the same colors (well mainly black) is used over and over again for different reasons. You can also see that there is a lot of overlap between the different sealants. One sealant can be used in many different applications. The thing to remember is, some of the sealants work better for certain applications.

Your best bet is to read the package and decide what is going to be best for your particular situation, no matter what brand or color it comes in.

  • Awesome answer. I just wanted to add that after 20+ years of experimenting, I use Right Stuff black for everything except turbo gaskets, (which I use ultra copper for) and thread locking. Right stuff will seal up NPT fittings carrying oil. I think AN and BPT (no tapered) are superior but if you are using NPT, right stuff will get it to seal and stay sealed.
    – Jim W
    Commented Apr 27, 2017 at 14:57

As an AZ shop owner for 39 years, we use blue silicone for typical gasket connections AND any cooling system or water system connections. We use red for exhaust manifolds and exhaust connections. We've never seen an O2 sensor that died because of silicone contamination. An O2 sensor is a battery, someday it will die just like the ones in your flashlight. We've found many stuck at 0.1 volt (range should be 0.1 to 0.5) and when we create a rich OR lean condition, they do not report that and then it is clear it is dead. We believe silicone contamination may have been true in the later 90's but not now. We use Permatex on threaded metal fittings and I use that at our ranch when connecting copper or galvanized pipes or fittings together. The success of your repair depends on the cleaning you do. We wash everything after we clean it to remove the solvent, the brake clean and carb clean residue. We also make sure the two surfaces are flat. If not, can I fix the divot with epoxy or can I grind/level a small bump or can I adjust for it.


All silicone is anerobic and dries/hardens due to the lack of moisture. ultra anything by locktite is sensor safe,red,grey,blue,black.

Proper use is not only dependant on the fluid to be sealed, the pressure has to be included, i.e. turbos.Ggaskets and sealants are equals and combined properly are the state of the art. Combined halfassedly are shit. Learn. If you glue one side of a gasket securely (gaskacinch) and grease the other side, it will never blow out or leak. It has an anchor on one side and it has give for thermal expansion with the grease on the other side. Even tourqued down it flexes but only so much under heat and pressure and returns to its initial strength, integrity when it cools down.

I love using ultra black for exhaust on hot rods that will be taken apart eventually, slather it in on both pipes and tighten the u-bolts just enough to where it doesn't twist anymore, let sit till tomorrow and drive. If you don't like the sound and want to switch, they come right apart. If you like it lasts for years and still comes apart easily when the mufflers rot out.

  • 1
    there are some situations ie high pressure where grease should never be used and the gasket should be fitted "dry".
    – Solar Mike
    Commented Jul 26, 2017 at 12:43

The right stuff is very dense silicone and doesnt flow well. But probably is the most common go to. a type i didnt see in you list , flowable silicone very thin fluid like silicone comes clear and is marketed to seal any gaps in winshield seals. Ive used it to seal roof repairs on some campers. Depending on the material. But i guess it works when used. No comebacks... The secret to a long served no leak gasket maker seal is surface preparation. Acetone, denatured alcohol or the stuff in your medicine cabinet will even work or a wax and grease remover all of witch wipe on wet then using another rag wipe off wet. Meaniing dont let it dry before its wiped over with a clean rag. If nothing else soap and water rinse well and a degreaser like windex that wont residue . Also there are 2 more common anaerobic gasket sealers. One is flexible the other more rigid and used widley for metal flanges anaerobic sealers have a reactive property to metal which helps the curing process in a no air environment and they are resistant to solvents and just about everything else.


To answer your questions:

Ignore colors--check specs online before you shop. Colors change by brand. Specs other than temperature rating:

- full cure time
- return-to-service time
- fluid type resistance*
- tighten-wait-torque vs torque-and-done

*Don't get too hung up on all the types. RTV for transmissions will be perfectly fine for your water pump. I just buy high-temp and use it for everything (no RTV for gasoline)

I personally dislike any gasket maker that cannot be torqued immediately. I can tolerate torquing and waiting for a cure, but I really don't want to have to go back for a second, final torque. One thing about RTV sealers, they have to cure before putting them back in service. If you want to assemble and use immediately, consider anaerobic sealer, or Right Stuff. See what the difference is below.

I want to clarify some misconceptions I'm seeing about RTV silicon and anaerobic products. This is important because they are not interchangeable in all situations. First of all, anaerobic means it cures "without air" (specifically, oxygen), not "without moisture". (http://instantca.com/articles/anaerobic-adhesives/)

This method of curing has several implications. Anaerobic products demand tight fitting, machined surfaces to seal off oxygen when tightly torqued. They will not seal gaps or voids, and will not seal loose fitting (stamped out) parts.

On the plus side, when used as intended they have a fast cure time--as little as 15 minutes--when used with accelerator/primers. And they don't require re-torque. They are the perfect choice when you need to get your assembly in use quickly.

Second, RTV silicon products cure by exposure to moisture, not lack of moisture. (https://acc-silicones.com/faq/rtv-silicone-meaning) Silicons are therefor not anaerobic products. One advantage of RTVs is their ability to bridge gaps between less-than-perfect mating surfaces. The drawback is that they can require up to 24 hours to cure before putting assemblies into service.

If you want the best of both worlds, Right Stuff is an elastomeric (moisture cure) that will seal most any surface, and can be put into service as soon as it is torqued.


I, as a GM Tech have always used they grey. GM uses exclusively grey for everything. I have never in my career had a leak or a leak come back after using it. I swear by it. it works on both coolant , oils, and diff fluids. It is better than any gasket. We use it in place of gaskets very very often. In the past in my younger years, I always had issues with blue stuff leaking when used on water pumps. I have seen many gaskets leak that were used in combination with a gasket. other than sealing corners or block mating surfaces that are bolted together at the seam, I do not recommend using gasket sealer on top of a gasket. its either / or. That is my .02. Black is also a good sealant to use, but grey is just simply the best. thats why most OEM's use it.

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