3 Times When Not to Use Moly Grease

Overview of Moly Grease and Its Limitations

Moly grease is a type of a lubricant that contains molybdenum disulfide (MoS2). This compound excels at reducing wear and friction, making it a versatile component in many lubricating oils, greases, and pastes. This is commonly used in heavy-load industrial or automotive machinery. But even on these, there are instances where you shouldn’t apply it.

Motor Hills | 3 Times When NOT To Use Moly Grease — ***Moly Grease***

Avoid using moly grease, with over 3% molybdenum disulfide, on components prone to sticking (e.g., worm gears) or at high speeds. Also, do not use this grease in applications exposed to excessive water ingress.

In this article, we will explain further why you wouldn’t want to use moly grease in these three situations. Afterward, we’ve included tips on how to use moly grease effectively for the best results.

When Not To Use Moly Grease

Keeping the components of any type of machinery well-lubricated is crucial to their longevity and performance, and moly grease is just one in a long list of options. However, it isn’t anything like your everyday WD-40.

This is a highly specialized grease used primarily on components within heavy-load machines that are exposed to extreme pressure and temperatures. Capable of withstanding pressure up to 500,000 psi and temperatures ranging from -18°C to 316°C (0°F to 600°F), it’s easy to think that this grease can do anything, but despite its impressive credentials, there are situations where it isn’t the ideal choice.

As we mentioned previously, you don’t want to use moly grease on applications:

With a high risk of sticking

That operate at high speeds

That experience excessive amounts of water ingress

If you were considering using this lubricant in one of the situations listed above, we invite you to read on as we explain why you’ll want to use an alternative instead.

Applications With High Risk of Sticking

The last thing you want from your moly grease is for it to actually cause your application to stick, rather than ensuring that everything runs smoothly.

While it is rare, this can happen with certain applications. The best examples would be in a slack adjustor, specifically one containing worm gears, and needle bearings in U-joints.

disc brake wheel bearing | times when not to use moly grease — ***disc brake wheel bearings***

This is because, as a solid lubricant, moly grease can cause worm gears to stick together due to the unique design where the worm wheel pairs with a worm mesh (or screw). When these components stick together, the odds of your slack adjustor failing increase substantially.

But that is just one example; so how can you know which applications are at a higher risk of sticking than others? This can be tricky and might take some experience gained from trial and error, but generally, moly grease is most effective in applications where there is significant sliding contact versus rolling. Common examples for this include journal or disc brake wheel bearings and axels.

Applications That Operate at High Speeds

Moly grease might be an excellent choice for applications that withstand extremely high temperatures or pressure, but if there’s one measurement where it isn’t the best choice, it’s with speed.

This particular lubricant works best when speeds are low and sliding contact is predominant, mainly because the moly particles within the grease are solid additives and, therefore, tend to be “larger than the fluid film developed by the base oil in a high-speed bearing.”

This is problematic since relative linear speed and lubricant viscosity are inversely related to each other, so the higher and application’s speed, the lower the viscosity required to adequately lubricate it. As a result, what tends to happen when you use moly grease in high-speed applications is the increased potential of point loading which, in turn, increases stress that can lead to fatigue and abrasive wear.

Applications That Experience Excessive Amounts of Water Ingress

Water resistance might be a major factor in your application and lubricant of choice. Moly grease is reliably water resistant, but there are instances where it poses an increased risk to nearby metallic components.

Molybdenum disulfide in this lubricant can sometimes corrode metal surfaces when exposed to excessive water. Since water ingress is already a concern, ensure the lubricant you choose doesn’t worsen the issue.

So, in these instances, you might want to consider a highly water-resistant or waterproof alternative.

Other Tips For Using Moly Grease

It’s also important to know when to avoid using moly grease, but there’s much more to learn for effective use of this lubricant.

Some additional tips we have for using moly grease include:

Understanding the difference between molybdenum disulfide grease (3% moly) and paste (40% moly) and their uses.

Understanding how moly content percentage alters which applications are ideal

Realizing that while moly grease performs best on metal-on-metal applications, it is compatible with a variety of materials

Never using moly grease for everyday lubrication and/or on low pressure applications

Another helpful tip is to refer to the user or manufacturer’s manual that comes with the machinery you’re trying to lubricate. Often, companies will list which components should be lubricated regularly and what type of lubrication they recommend most. If they specify molybdenum disulfide grease (abbreviated as ‘M’) or paste (abbreviated as ‘MP’), follow their guidelines.

Optimal Use of Moly Grease

Moly grease extends machinery life by reducing wear on moving parts and improving efficiency by minimizing friction. However, its effectiveness depends on selecting the right applications for this specific type of lubrication. In summary, avoid using moly grease in:

Applications with a high risk of sticking, such as worm gears.
High-speed applications where fluid film lubrication is critical.
Environments with excessive water ingress to prevent corrosion.

Always consult the manufacturer’s guidelines to ensure you select the best lubricant for your machinery. By applying this knowledge, you can use moly grease more effectively and confidently in the future.

3 Times When NOT To Use Moly Grease

Overview of Moly Grease and Its Limitations