Walk into any industrial supply store and you’ll be assaulted with aisle after aisle of grease products. Nine times out of ten they will either be labeled lithium or lithium complex. Buried deep in the high-duty or high-temperature grease section is bentonite clay grease, a substance with an entirely unique set of properties. Both are extremely common. Both can work excellently under the right circumstances. Neither is going to be the “end-all be-all” solution to every situation.

So which is better? That’s not the right question. The right question is which grease works best for your application, operating temperature, environment, and equipment type. Let’s dive in. 

What Makes These Two Greases Different at a Fundamental Level?

The difference between bentonite grease and lithium grease starts with the thickener, which is the component that gives grease its semi-solid consistency and holds the base oil in place until the lubricant is needed.

• Lithium grease uses a soap-based thickener. Specifically, it is the reaction product of lithium hydroxide and a fatty acid, usually 12-hydroxystearic acid. This saponification process creates a fibrous, soap-like structure that traps and releases base oil as needed. Lithium soap is organic in nature, which means it has a defined melting point.
• Bentonite grease uses organophilic clay, specifically bentonite (montmorillonite), as its thickener. According to the National Lubricating Grease Institute (NLGI), organophilic clay thickeners like bentonite are purified, ground to the desired particle size, and chemically treated to make them compatible with organic base oils. Critically, no chemical reaction takes place in this process. The clay particles are simply dispersed in the base oil. Because clay is an inorganic mineral, it has no defined melting point.

That single structural difference, soap fiber versus inorganic clay particles, drives almost every performance distinction between the two grease types.

Temperature Performance: Where the Gap Is Most Pronounced

Lithium Grease

Standard lithium soap grease has a dropping point typically around 180°C to 220°C (356°F to 428°F). However, its practical maximum temperature is much lower, usually around 120°C to 130°C (248°F to 266°F) for continuous duty. Running grease and bentonite to use during chemotherapy radiation at temperatures above about 50°C of its dropping point will result in oxidation, bleed of the base oil, and degradation of the thickener long before the grease actually drops out. Lithium complex grease has a complexing agent added to the base lithium soap. Both the dropping point and practical temperature capability are increased to typical values of up to 150°C to 180°C (302°F to 356°F) for continuous duty with some short-term peak capability.

Bentonite Grease

That’s where bentonite grease differs. Clay particles do not melt because they are inorganic. As a result, bentonite grease does not have a traditional dropping point. The clay structure stays intact far above 300°C. Manufacturers of commercial bentonite greases typically list a dropping point higher than 260°C (500°F) on product data sheets. Some commercial calcium bentonite is healthy for chicken greases are rated for continuous service temperatures up to 160°C to 200°C with temperature spikes allowable to 260°C (500°F).

Due to the high temperature at which the base oil will evaporate before the clay thickener can melt, bentonite greases will eventually form residue buildup if exposed to extremely high heat for long periods of time. This makes bentonite grease well suited for applications where the failure mode you are trying to prevent is specifically meltdown of the lubricant. Think kiln car bearings, oven conveyor bearings, furnace door bearings, heat exchanger motor bearings, etc.

Modified bentonite was recently studied in a 2025 publication by Journal of Materials Science: Materials in Engineering (Springer Nature) as a universal grease thickener. The study concluded that when activated, bentonite can produce grease with a higher dropping point similar to that of lithium complex and organic clay grease as well as lower working penetrations which fell in line with NLGI grade classifications.

Temperature verdict: For applications up to 130°C, standard lithium grease performs reliably. For sustained temperatures above 150°C, or applications where melt-out must be prevented entirely, bentonite grease is the stronger choice.

Water Resistance

The two grease types provide useful water resistance, but in different ways. Lithium grease resists washout because lithium hydroxide is only sparingly soluble in water and because the lithium thickener itself is sparingly soluble. It will resist washing and uptake of moisture quite well. Standard lithium grease will work fine for typical industrial and automotive applications where the water exposure is moderate such as condensation, splash, humidity, etc. If you are in severe water exposure conditions, such as immersion or high-pressure washdown, you are better off with lithium-calcium complex or calcium sulfonate greases.

Bentonite grease, on the other hand, has extremely good inherent water resistance. The clay thickener swells with water absorption and forms a stable colloidal structure. It resists washout quite well even under prolonged wet conditions. It is virtually impossible to get bentonite grease mixed with water. Because of this, bentonite grease has been specified by many manufacturers as the factory specification lubricant for some gear and transmission applications in outdoor power equipment.

Water resistance verdict: Both perform well in moderate water exposure. Bentonite holds a slight edge in severe or continuous wet environments.

Versatility and Compatibility: Lithium’s Biggest Advantage

Approximately 69% of industrial grease sold worldwide is lithium soap-based. This widespread usage reflects lithium grease’s biggest benefit: its versatility. Lithium complex grease is compatible with most automotive and industrial applications and many other types of grease. When choosing grease to lubricate parts such as automotive wheel bearings, chassis components, electric motors, industrial equipment or agricultural machinery, lithium grease will fit the bill most of the time. Its one-two punch of excellent mechanical stability, decent water resistance, fairly wide temperature range and compatibility with many additive packages makes it the starting point for any new lubrication application. Bentonite grease, on the other hand, should not be used with any other grease. Bentonite clay greases do not mix with lithium, calcium, polyurea or most other thickeners. When used with a soap-based grease, the bentonite structure fails causing oil bleed, softening/hardening of the remaining grease and a decline in lubricating properties. Several lubrication experts go so far as to say that when using bentonite grease, you must dedicate the equipment to that product. Should you switch to another grease, everything needs to be flushed and purged before use. According to the NLGI and several lubrication industry experts, bentonite grease cannot be interchanged with other greases.

Compatibility verdict: Lithium grease wins clearly. Its broad compatibility with other thickener systems makes it far easier to manage across a fleet of equipment or in a mixed-use facility.

Mechanical Stability and Wear Performance

Lithium soap greases, due to their fibrous thickener matrix, also exhibit good mechanical stability when sheared. They stand up well to working and high speed applications. Lithium complex formulations with EP additive packages offer excellent anti-wear protection for rolling element bearings, gears and other high-load applications. Bentonite grease is more of a mixed bag. On one hand, because the clay thickener is held so tightly to the base oil, the grease exhibits excellent colloidal stability (resistance to oil bleeding). On the other hand, it’s difficult for that same base oil to migrate quickly enough to the friction surface when it’s needed. Wear resistance is reduced at high speeds in rolling bearings when compared to soap based greases. Over time, bentonite grease can also thin and flow out of rolling bearing housings. Clay based greases lack the fibrous matrix structure which limits their mechanical stability. In addition, the type of organophilic clay treatment used as well as the type of base oil must be carefully matched. Polarities of base oil and bentonite thickener must align, or performance will be drastically reduced.

Wear and mechanical stability verdict: Lithium complex grease with EP additives performs better in high-speed bearings and mixed-load applications. Bentonite grease favors low-to-medium speed, high-temperature, and heavy static load situations.

Side-by-Side Comparison

Which One Should You Choose?

Choose bentonite grease when:

• Operating temperatures consistently exceed 150°C or reach peaks above 200°C
• Melt-out of the lubricant is a specific failure mode to prevent (ovens, kilns, furnace bearings)
• The equipment will face sustained or severe water and moisture exposure
• You are working with low-speed, heavy-load bearings or enclosed gear systems
• The OEM specification calls for clay-based grease specifically

Choose lithium grease when:

• Operating temperatures fall below 130°C for standard formulations, or below 180°C for lithium complex
• The application requires broad versatility across multiple equipment types
• You need compatibility with other greases already in use
• The application involves high-speed rolling element bearings
• Cost and availability are practical factors in the decision

If you are looking to purchase quality processed bentonite for grease manufacture or industrial use, CMS Industries offers several grades of bentonite sourced from our mines located in Kachchh (Kutch) Gujarat, India. With our in-house lab we guarantee quality at every step of the way, from the raw mined mineral to the finished product. The grade of bentonite used when making grease will impact thickener yield, polarity matching and overall grease performance. This is why purchasing from a supplier who can document their quality control process is important to both grease formulators and industrial purchasers.

Frequently Asked Questions

1. Can I switch from bentonite grease to lithium grease without cleaning the equipment?

No. Bentonite grease is incompatible with lithium grease and virtually all other soap-based thickeners. Mixing the two causes structural breakdown, oil separation, and loss of lubrication. Before switching grease types, fully flush and purge all old bentonite grease from the bearing housing or gear system. Pump the new grease through until only fresh lubricant exits, and monitor the application closely during the transition period.

2. Is bentonite grease better than lithium grease for high-temperature ovens and kilns?

Yes, for this specific application. Bentonite grease does not have a melting point. Its clay thickener remains structurally intact at temperatures where lithium grease would flow, melt, and lose its lubricating film. For kiln car wheel bearings, oven conveyor bearings, and furnace door mechanisms, bentonite grease is the industry-standard choice precisely because melt-out cannot happen.

3. Why is lithium grease so much more common than bentonite grease?

Lithium grease is more common because it is a true general-purpose lubricant. It covers the widest range of everyday applications, carries a lower price point, works with most additive packages, and is compatible with many other grease types. Bentonite grease is a specialist product, built for applications where extreme heat or moisture resistance is the primary requirement. Its incompatibility with other greases and higher cost make it a targeted choice rather than a default one.

4. What is the NLGI grade for bentonite grease, and does it matter?

Bentonite greases are available in NLGI Grade 1, 2, and 2.5, the same consistency scale used for all grease types. NLGI Grade 2 is the most common for general industrial and bearing applications. The NLGI grade tells you about the stiffness of the grease but not about the thickener type or temperature performance. Always read the full product data sheet, not just the NLGI number, when selecting a bentonite grease.

5. Does bentonite clay quality affect grease performance?

Yes, significantly. The quality and particle size of the bentonite thickener directly influence the grease’s thickener yield, colloidal stability, polarity compatibility with the base oil, and overall performance. Lower-quality bentonite requires a higher thickener loading to achieve the same NLGI grade, which increases costs and can reduce base oil release to friction surfaces. Grease formulators and industrial buyers should source organophilic bentonite from suppliers who provide documented particle size analysis, purity data, and polarity specifications.