Of the products that Loctite produces, Loctite 242 and 243 are two of their most popular. This is a company that produces hundreds of products, and these stand tall above them all, and that’s saying something about how great these are.
There’s a good reason these two are their most popular. They are what’s called “Threadlockers“, a type of adhesive commonly used by mechanics.
The difference between Loctite 242 and Loctite 243 is that Loctite 243 is an upgraded version of the popular Loctite 242. When using 243, you aren’t likely to notice any difference when applying Loctite 243, but where 243 shines over 242 is in its oil tolerance, which is improved over Loctite 242.
As I said, you’re unlikely to notice the difference between these two products, and that is entirely true, and if you’ve never used these before, you really won’t see a difference when you use them.
But there is a difference.
If you’ve been using Loctite 242, then I’m going to show in just a few reasons why you should upgrade to Loctite 243.
Why Loctite 243 is better than 242
For me, there’s no doubt that blue Loctite 243 is a superior option to 242, even Loctite themselves have stated that this is an upgraded version.
But the majority of people don’t want to make the upgrade, they’ve grown accustomed to Loctite 242, they know it works so change it? I mean, if you’ve already purchased 242, why waste the extra cash on something that’s the same, right?
Yeah, it’s similar, but it’s better much better, and it will make your life easier in the long run.
While on the face of things, the two are very similar, with the differences being minimal, as I said you aren’t likely going to notice the difference initially. Even I’ll pick up Loctite 242 from Amazon if I am going to buy it, why? well, it’s typically the easiest way for me to get hold of it and it’s usually pretty cheap.
- MIL-S-46163A for Existing Designs
Right, let’s get down to why you should upgrade to 243, why it’s the better choice for you than going for Loctite 242.
- It’s stronger – If you haven’t used these two products at all or often, then take it from someone who has used both extensively. Loctite 243 is stronger than 242. Not by a great deal mind, but it’s noticeably stronger, in my opinion.
- It’s oil resistant – The biggest reason to upgrade is that 243 is much more oil resistant than 242. Loctite has listened to the feedback from consumers and decided to produce a product that can be easily used on threads.
- It’s great for lazy people (myself included) – If you are happy to clean every thread before you apply a Threadlocker then feel free to stick with using 242. But if you want to save a lot of time, then the main benefit of using 243 is that it’s oil resistant, this means that it doesn’t matter if there’s still some oil on your threads, you can apply 243 straight away without taking time to clean up first.
These are the main reasons that I prefer to use 243 over 242. Add to that that Loctite 243 isn’t particularly expensive either, so cost isn’t going to be a huge factor, and yes, I am painfully aware of how all those difference adhesives quickly add up in price.
When it comes to Loctite 242 vs 243 they both still work great for medium-strength applications such as using Loctite for thread locking:
- rocker studs
- oil pans
- disc brake calipers
- pulley assemblies
- valve cover bolts
- lock washers
- lock nuts
- carburetor studs
- hand tools
Other Loctite Threadlockers I recommend
There is a raft of other Loctite products out there, but I tend to use their Threadlockers (like the majority of people, which is why they are Loctite’s top products). So, I feel like I am in an excellent position to talk about the best Loctite Threadlockers that are currently on the market, and hopefully, help you understand the differences between them.
Loctite 221 & 222 – Low strength
Loctite 221 and 222 are great options for those of you who are looking for a low strength Threadlocker – these are suitable for use on small threads up to a maximum size of M12. These have a low viscosity, which means that these are pretty thin, which works well for a Threadlocker that’s designed for small threads.
- Prevents vibration loosening of small screws and fasteners
- Low strength noncorrosive formula threadlocker
- Removable with hand tools for easy disassembly
- Works with small screws under 1/4″ including threaded fasteners
- Can withstand up to 300°F
- Set time is quite fast – 10 minutes, sometimes even less
Loctite 272 & 278 – Temperature Resistant
If you need something that can handle heat and also has a medium viscosity. Somethings that’s designed to be used in relatively high strength applications, then look no further than Loctite 272, this is your best bet. It’s designed to be used for permanent thread locking, so you know that this is going to be a high strength product.
- Fastener size:
- 3/8″ to 1 1/2″
- Maximum heat:450°F
- Fixture time: 40 minutes – 1 hour
- example uses: Crankshaft bolts, shock bolts, ring gear, idler bearings
Loctite 270 & 276 – High Strength
If you want to lock threads up permanently, something that’ll require a breaker bar to crack, then you’ll need to opt for a high strength Threadlocker. Loctite 270 and 276 are what you need, and these are two high strength Threadlockers that fulfill those criteria.
Why would you need a high strength Threadlocker? It’s essential to use a high strength Threadlocker when you are dealing with bolts that are going to vibrate a lot, as vibration tends to undo bolts.
Locktite 290 – Wicking
Wicking Threadlockers can be confusing, but they’re designed to be extremely low viscosity so that they can penetrate the existing bolts on threads. Why? So that you can apply the Threadlocker itself without needing to disassemble anything, it will seep down into the threads and hold those bolts tight.Amazon product
Frequently asked questions
Does Loctite 242 need primer?
Unfortunately, the original Loctite 242 does need primer, and I suggest upgrading to Loctite 243, which is a medium strength nut locker, which prevents fasteners when properly-torqued from loosening from vibration but allows hand tool disassembly. 243 Primerless will adhere to inactive metals without the need for a primer.
Which Loctite is strongest?
Red Threadlocker is the highest strength. It cures fully in 24 hours, So look for Loctite 270 or 276. These are so strong that you need heat to disassemble them.
Is Loctite 242 oil resistant?
No, if you are going to be able to use Loctite threadlocker 242 on threads, which still have oil on them. You will need to take the time to remove any remaining oil before applying Loctite 242. However, Loctite has an upgraded version of 242, Loctite 243, which has oil tolerance so that you can use it, even with oil present.
How long does Loctite 243 take to dry?
Once you’ve assembled the parts, tightened and torqued correctly, it takes around 10 minutes to set and will fully cure in 24 hours.
There are hundreds of different Loctite products to chose from, and there are other Loctite Threadlockers out there, so I can’t compare them all. Plus, it would be a bit wrong to recommend products I haven’t used myself.
Hopefully, I’ve covered the differences between Loctite 242 vs 243. Regardless of your needs, it’s worth using a Loctite brand threadlocker for the best overall performance. You also look at Permatext – Loctite’s biggest competitor. Though for me, I’ll always reach for Loctite before anything else.
If you have any questions, please drop a comment below.