Lubricants are commonly used especially in the automotive sector (e.g. engine oils and gear oils) as well as in industry (gear oils, hydraulic oils, gearbox and slideway oils, chainsaw oils, compressor oils, lubricating oils, thermal oils, turbine oils, fats, hardening oils, heat treatment oils and many more). However, the total volume of industrial lubricants sold worldwide is smaller than that of engine and transmission oils for the transport sector.

Lubricants are a blend of base oils and, depending on their use, additives. The proportion of base oils in the finished product is usually between 70% and 95%. Additives have multiple functions, for example to prevent foam formation, to clean, or improve the viscosity index. Although often only referred to as a lubricant, in addition to lubrication to reduce friction and wear, power transmission, cooling, and vibration control, lubricants must also perform many other tasks – including the heat transfer of oil, fine sealing and corrosion protection. In addition, lubricants neutralize aggressive combustion products.

The basic tasks of lubricants can thus be summarized as follows:

• Lubrication
• Cooling
• Sealing
• Cleaning
• Protection

Types of base oils and lubricants

Base oils can be of mineral origin, where they are obtained from crude oil using conventional refining processes. Here, products of different viscosities can be manufactured depending on the area of application.

Furthermore, there are non-conventional base oils. These are distillation products, which, although also commonly obtained from crude oil, are physico-chemically post-treated: Their molecular chains are broken down and reassembled using “hydrocracking.”

Beyond this there are the synthetic base oils. Unlike mineral oil they do not consist of a variety of hydrocarbons, but of similar compounds. Synthetic oils are obtained by chemical conversion of olefins. They are of very high quality, and also very resistant to aging, for example. They also have lower evaporation losses, a high pressure absorption capacity, and cause only very low sludge formation. And due to their lower phosphorus content, they protect the catalytic converter when used in gasoline engines.

When additives are added to these base oils, we get the above-described lubricants.

Besides the mineral oil-based and synthetic lubricants there are also biological lubricants based on vegetable oil and vegetable oil-based synthetic esters. They significantly differ from mineral oil-based lubricants in their technical properties: They need less additives to support their lubricating properties and are also more prone to oxidation and hydrolysis, and therefore require a higher addition of additives to improve durability. Moreover, vegetable oil products can also only be used at operating temperatures of between -10°C and 70°C. Their advantage is their biodegradability, which is why often in nature, only biological chain lubricants may be used – for example for chainsaws in the forest. For rapidly biodegradable chainsaw lubricants, for example, there is the RAL-UZ 48 eco-label. A substance is classified as rapidly biodegradable if it is at least 60% degraded within 28 days according to the OECD 301 (B-D, F) test process.

Quality criteria for lubricants

On the one hand, there are standardization and classification systems for lubricants, e.g. SAE, API, ACEA, ILSAC and OEM for car and commercial vehicles:

• SAE = Society of Automotive Engineers (classification by viscosity properties, such as 5W-30)
• API = American Petroleum Institute (oil classification after laboratory and engine testing)
• ACEA = Association of Constructors of European Automobiles (oil classification after laboratory and engine testing; successor system to the CCMC since 1996)
• ILSAC = International Lubricant Standardization and Approval Committee
• OEM = Original Equipment Manufacturer (various requirements and provisions from the manufacturer, i.e. each manufacturer “approves” these lubricants in accordance with their requirements and permits their use)

Manufacturer approvals (OEM approvals) are also issued for industrial lubricants. This means that the manufacturer issues a recommendation for a specific lubricant by name, thereby indicating that this product can be used in all or in certain aggregates produced by this manufacturer.

In addition, for common applications, requirements and classifications are also determined in national and international standards: in Germany primarily in the DIN standards, and internationally mainly in the ISO standards. Examples include DIN 51524 51524 Part 2 for hydraulic oils, CLP DIN 51517 Part 3 for gear oils, DIN 51515 Part 1/Part 2 for turbine oils, ISO VG 46, ISO VG 68, etc., ASTM D 3306 and ÖNORM C2030. Another testing method used is based on the biodegradability of oil-soluble products according to CEC-L-33-A-93. A full list of standards and classifications would be too long to include here.

In the industrial processing of foodstuffs, special approvals are necessary due to the hygienic requirements for physiologically compatible lubricants (such as natural fats and oils), for example by the U.S. Food and Drug Administration (FDA) or Department of Agriculture. Quality requirements are set out in the IFS (International Food Standard) and BRC (British Retail Consortium) regulations.