Lubricating greases are colloidal suspensions consisting of a thickening agent in a liquid lubricant (mineral oils, synthetic oils). To improve specific properties, various types of additives are mixed with the lubricating greases. Such additives include:
Oxidation and corrosion inhibitors, adhesion promoters, anti-wear and high-pressure protection additives (EP additives), friction modifiers (graphite, molybdenum disulfide, etc.).
The right combination of base oils, thickening agents and type of additive to achieve specific lubricating grease properties requires extensive development work.
Lubricating grease should reduce friction and wear, prevent corrosion, seal lubrication points and be resistant to operating temperatures that occur. When selecting suitable lubricating greases, in addition to the operating conditions, environmental influences, lubricating intervals, etc., the use properties of the greases should also be taken into consideration in particular.
The chemico-physical analysis values provide information on the composition and the potential applications of the lubricating greases. The most important parameters are:
Consistency (moldability of the lubricants), resistance to milling, thermal loading capacity, drop point, temperature use ranges (highest and lowest permissible use temperature), anti-corrosion properties, resistance to oxidation and aging, oiliness, anti-wear properties, water resistance, miscibility, compatibility with sealing material
Manufacturers and consumers refer to the lubricating greases according to different aspects. Thus, it is customary that greases are classified and referred to by consumers according to the use in practice, such as e.g. rolling-element bearing greases, lubricating greases, water pump greases, etc.In contrast, the lubricating greases are classified by the manufacturers according to the thickening agent used. These product labels such as calcium soap greases, sodium soap greases and lithium soap greases have the advantage that the type of soap used, which essentially defines the character of the grease and the usage limitations, is obvious.
The lubricating greases are classified according to their worked penetration in NLGI consistency classes (penetration stages).
With the worked penetration, the penetration is measured after a precisely defined kneading process (shearing stress). As the worked penetration value increases, the NLGI consistency number decreases, and the grease becomes softer.
The relationship between consistency and penetration is also shown by the table below.
Connection between consistency and penetration
Worked penetration (0.1mm)
For use in Mercedes-Benz vehicles, the following lubricating greases are approved:
Liquid greases, Sheet 264.0 (Lithium-12-OH-stearat greases), NLGl class 00/000
The liquid greases for central lubricating systems are semi-fluid lubricating greases with good anti-corrosion properties.
Liquid greases must have good displacement and expansion properties and have good flow properties in the temperature use range. Application range approx. -30℃ to +120℃.
High-temperature rolling-element bearing greases, Sheet 265.1, (Li complex soap greases), NLGI class 2
These are greases which are specifically customized to the higher demands of passenger vehicle front wheel bearings, have a high drop point and excellent resistance to milling. Therefore, they are suitable for continuous use from -30℃ to +170℃ and have provided satisfactory results after tests in practice over many years for lifetime lubrication of car front wheel bearings.
Lubricating greases, Sheet 266.0 (calcium soap greases), NLGI class 1
These greases are water resistant and water repellent. Lubricating greases provide satisfactory lubrication results for commercial vehicle chassis component parts at temperatures between approx. -30℃ and +70℃. During the time of use, the greases must not oxidize or change inadmissibly in terms of consistency.
Long-term greases, Sheet 266.2, NLGI class 2
Lubricating greases based on lithium soap with the addition of molybdenum disulfide (MoS2). Application range approx. -25℃ to +110℃, and for a short period up to +130℃.
For lubrication points that place increased demands on the high pressure and long-term lubrication properties of greases due to the design and operating conditions.
Multipurpose greases, Sheet 267.0 (lithium soap greases), NLGl class 2
Multipurpose greases are to be used for all lubrication points for which no particular special greases are stipulated. Application range approx. -30℃ to + 130℃. Lithium soap greases combine the advantages of calcium and sodium soap greases. They have good overall properties, higher drop point, good water and oxidation stability, adequate anticorrosion properties, high milling stability and are therefore suitable for longer service lives.
Wheel bearing greases, Sheet 267.1, NGLI class 2 for special cases of application on wheel bearings in service
The complex grease stipulated for the center suspension at the spring saddle of double axle assemblies with spur gear axles is distinguished by high milling stability, good water stability and oiliness and corresponding anticorrosion properties. Application range approx. -10℃ to +90℃.