Selecting the correct grease is one of the most underestimated decisions in maintenance engineering. The wrong choice can lead to premature bearing failure, overheating, contamination, and costly downtime. Understanding the different lubricant grease types available on the market is therefore essential for technicians, fleet managers, and procurement specialists who want to extend equipment life and reduce operational costs.
In this comprehensive guide by Merouris, we’ll examine the main lubricant grease types, their composition, the NLGI consistency classification system, and how to match the right grease to your specific application.
What Is Lubricating Grease and How Does It Work?
Lubricating grease is a semi-solid lubricant composed of three primary elements: a base oil (typically 70–90%), a thickener (5–20%), and a package of performance additives (0–10%). The thickener acts like a sponge that holds the oil in place, releasing it gradually under load and motion to lubricate moving surfaces.
Unlike oils, grease stays in position, seals out contaminants, and provides long-lasting protection in components where re-lubrication is infrequent or impractical. The performance of any grease depends on three key technical parameters:
- Base oil viscosity — determines lubricating film strength
- Thickener type — affects temperature resistance and water tolerance
- Drop point — the temperature at which the grease loses its structure and flows
Greases are classified by consistency using the NLGI grading system, developed by the National Lubricating Grease Institute, which we’ll explore in detail later in this article.
The Main Lubricant Grease Types Explained
The most common way to categorise greases is by their thickener chemistry, since this defines their thermal, mechanical, and water-resistance properties.
Lithium-Based Grease
Lithium grease is the most widely used grease worldwide, accounting for approximately 70% of the global market. It offers excellent mechanical stability, good water resistance, and a typical operating range of −20 °C to +120 °C. Lithium complex variants extend this range up to +150 °C or higher, making them suitable for wheel bearings, chassis components, and general industrial machinery.
Calcium-Based Grease
Calcium grease is renowned for its outstanding water resistance, making it ideal for marine and wet environments. Traditional calcium soap greases have a limited temperature range (up to +60 °C), but modern calcium sulphonate complex greases can operate beyond +180 °C while delivering excellent corrosion and EP performance.
Sodium-Based Grease
Sodium grease offers good high-temperature performance (up to +120 °C) but poor water resistance — water washes it out easily. It has largely been replaced by lithium and complex greases, although it still appears in some legacy industrial applications.
Polyurea Grease
Polyurea grease uses a non-soap organic thickener and excels in high-speed bearing applications, particularly sealed-for-life electric motor bearings. It offers excellent oxidation stability, long service life, and an operating range up to +170 °C. According to SKF’s bearing lubrication guidelines, polyurea is the preferred choice for many premium sealed bearings.
Aluminium Complex Grease
Aluminium complex grease combines high-temperature capability (up to +160 °C) with excellent water resistance and shear stability. It’s commonly used in food-grade NSF H1 formulations and steel mill applications where heat and moisture coexist.
Bentonite (Clay-Based) Grease
Bentonite grease is a non-melting grease — it has no true drop point, meaning it can withstand extreme temperatures (over +200 °C) without liquefying. It’s used in furnaces, kilns, and oven conveyors, but its mechanical stability and water resistance are limited.
Synthetic Grease (PAO, PAG, Silicone)
Synthetic greases use engineered base oils such as polyalphaolefins (PAO), polyalkylene glycols (PAG), or silicones. They offer:
- Wider operating temperature ranges (−50 °C to +200 °C)
- Superior oxidation resistance
- Extended re-lubrication intervals
- Excellent performance in extreme conditions
These premium greases are increasingly specified for critical industrial assets, wind turbines, and aerospace components.
Classification by Application
Beyond thickener chemistry, lubricant grease types are also categorised by their intended end use.
Multi-Purpose Grease
Designed for general lubrication across automotive and light industrial applications, multi-purpose grease typically combines lithium thickener with EP additives and corrosion inhibitors. It offers a balanced compromise rather than peak performance in any single area.
High-Temperature Grease
High-temperature grease uses thickeners and base oils engineered to maintain film strength above +150 °C. Common chemistries include polyurea, aluminium complex, and PFPE (perfluoropolyether) for extreme cases reaching +250 °C.
Extreme Pressure (EP) Grease
EP grease contains additives such as molybdenum disulphide (MoS₂), graphite, sulphur-phosphorus compounds, or zinc that form sacrificial films under high loads. It’s essential for heavily loaded gears, open gears, and shock-loaded bearings.
Food-Grade Grease (NSF H1)
Greases certified to NSF H1 standards are formulated for use in food and beverage processing where incidental contact with food may occur. These products use food-safe base oils and thickeners and are registered through NSF International.
Discover our complete range of food-grade lubricants, or read our in-depth guide on food-grade lubricant selection for safe machinery maintenance.
Marine / Waterproof Grease
Marine grease combines water-resistant thickeners (typically calcium sulphonate or aluminium complex) with strong corrosion inhibitors to protect components exposed to salt water, such as boat trailers, propeller shafts, and dockside equipment.
NLGI Grade System: Understanding Grease Consistency
The NLGI system classifies grease by consistency — essentially, how soft or hard it is. Consistency is measured using a cone penetration test defined by ASTM D217, which drops a standardised cone into the grease and measures penetration depth in tenths of a millimetre.
| NLGI Grade | Penetration (mm/10) | Consistency | Typical Applications |
| 000 | 445–475 | Fluid | Enclosed gearboxes, central lubrication systems |
| 00 | 400–430 | Semi-fluid | Gearboxes, low-temperature centralised systems |
| 0 | 355–385 | Very soft | Centralised lubrication, low-temperature use |
| 1 | 310–340 | Soft | Centralised systems, chassis lubrication |
| 2 | 265–295 | Medium (most common) | Wheel bearings, general industrial use |
| 3 | 220–250 | Firm | High-temperature bearings, vertical shafts |
| 4 | 175–205 | Very firm | Specialised sealed applications |
| 5 | 130–160 | Hard | Block grease, specialised plain bearings |
| 6 | 85–115 | Very hard | Block grease for specific industrial uses |
NLGI Grade 2 is the global default for most automotive and industrial applications, balancing pumpability and load-bearing performance.
How to Choose the Right Lubricant Grease Type for Your Application
Selecting the optimal grease requires evaluating several technical and operational factors:
- Operating temperature range — both minimum start-up and maximum continuous temperature
- Load conditions — standard, heavy, or shock loads (EP additives required?)
- Speed factor (n·dm) — high-speed bearings need lower-viscosity base oils
- Environmental exposure — water, dust, chemicals, or extreme cleanliness requirements
- Re-lubrication intervals — sealed-for-life vs frequently greased components
- Compatibility with previously used grease and seal materials
Bearings are particularly demanding components — for a deeper analysis on this topic, read our guide on the importance of choosing a lubricant for bearings.
For detailed selection methodology, Machinery Lubrication and the Society of Tribologists and Lubrication Engineers (STLE) publish excellent technical resources used by lubrication professionals worldwide.
Grease Compatibility: What You Need to Know Before Mixing
Mixing incompatible greases can be catastrophic for equipment. When two incompatible thickener systems combine, the resulting blend may soften dramatically, harden, or lose its ability to retain oil — leading to lubricant starvation and bearing failure.
General compatibility rules:
- Lithium and lithium complex are generally compatible with each other
- Polyurea is incompatible with most soap-based greases
- Calcium sulphonate is compatible with most other thickeners
- Bentonite (clay) is incompatible with nearly all soap-based greases
Always consult a grease compatibility chart from the manufacturer before switching products. When in doubt, purge the old grease completely before introducing a new one.
Frequently Asked Questions
What are the different types of grease lubricants?
The main lubricant grease types are classified by their thickener chemistry: lithium, lithium complex, calcium, calcium sulphonate, sodium, aluminium complex, polyurea, and bentonite (clay). Each offers distinct performance characteristics in terms of temperature resistance, water tolerance, mechanical stability, and load-bearing capacity. Greases are also categorised by application — multi-purpose, high-temperature, extreme pressure (EP), food-grade (NSF H1), and marine grease — and by consistency using the NLGI grading system from 000 (fluid) to 6 (very hard).
What are the 4 types of lubricants?
The four primary categories of industrial lubricants are: (1) Oils — liquid lubricants used in engines, hydraulics, and gearboxes; (2) Greases — semi-solid lubricants combining oil, thickener, and additives for bearings and chassis components; (3) Dry lubricants — solid materials such as graphite, molybdenum disulphide (MoS₂), and PTFE used where liquids would attract contamination; and (4) Penetrating fluids — low-viscosity products designed to free seized parts and displace moisture. Each category serves specific applications based on operating conditions, load, temperature, and environment.
Which grease is thicker, 0 or 00?
NLGI Grade 0 grease is thicker than NLGI Grade 00 grease. The NLGI scale runs from 000 (most fluid) to 6 (hardest), so as the number increases, consistency increases. Grade 00 has a worked penetration of 400–430 mm/10, while Grade 0 measures 355–385 mm/10 — the lower the penetration value, the thicker the grease. Both grades are considered very soft and are typically used in centralised lubrication systems, enclosed gearboxes, and low-temperature applications where the grease must flow easily through long pipework.
Is WD-40 a grease or lubricant?
WD-40 is neither a true grease nor a long-term lubricant — it’s primarily a water-displacing penetrant (the “WD” stands for “Water Displacement”). The original formula provides light, temporary lubrication and excels at freeing seized parts, displacing moisture, and cleaning. However, it evaporates relatively quickly and lacks the load-bearing capacity, longevity, and temperature stability of dedicated greases or lubricating oils. For ongoing lubrication of bearings, hinges, or mechanical components, you should use a purpose-formulated grease or oil suited to the application.
Choosing Wisely
Choosing among the available lubricant grease types is a decision that directly impacts equipment reliability, maintenance costs, and operational efficiency. Understanding thickener chemistry, NLGI consistency grades, and compatibility considerations allows you to specify the right grease the first time — avoiding premature failures and unplanned downtime.
If you’d like expert guidance in selecting the optimal grease for your machinery, explore the full range of industrial and automotive lubricants available at Mercouris. Our technical team can help you match the correct lubricant grease types to your specific application requirements.