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Lubricants: Focus on Variety and Function

Lubricants are essential components in industry, mechanical engineering, and automotive technology. Depending on the application, they are generally divided into two main categories: industrial lubricants and automotive lubricants. Each of these areas contains numerous specialized products tailored precisely to specific technical requirements.

Although the overall consumption of industrial lubricants is lower than that of engine and transmission oils in the transport sector, the product range in industry is significantly broader. This is due to the wide variety of applications requiring carefully optimized lubricant solutions.

Despite their differences, all lubricants perform five key functions:

  • Reducing friction and protecting components from wear

  • Dissipating heat and preventing overheating

  • Supporting sealing systems and blocking contaminants

  • Binding residues and preventing deposits

  • Providing corrosion protection for long-term surface preservation

Choosing the right lubricant is therefore critical to protecting your machinery, extending service life, and maximizing operational efficiency.

 

Base Oils: The Quality Foundation of Modern Lubricants

As a specialized supplier of high-quality lubricants, we know that selecting the right base oil is crucial for product performance, durability, and environmental compatibility. Whether for industrial or automotive applications, the chosen base oil largely determines the final lubricant’s effectiveness.

Generally, base oils are divided into four main types:

  • Mineral base oils – refined from crude oil

  • Synthetic base oils – chemically engineered products

  • Re-refined oils – regenerated from used lubricants

  • GTL base oils (Gas-to-Liquid) – synthesized from natural gas

Mineral Oils: Proven Standard for Many Applications

Most lubricants worldwide are still based on mineral oils, derived from the refining of crude oil. In addition to traditional virgin base oils, re-refined oils are increasingly used. These oils are recovered from used lubricants and regenerated into high-quality base oils – contributing significantly to resource conservation.

Synthetic and GTL Oils: For Maximum Performance

Synthetic base oils are produced through controlled chemical processes, offering consistent quality, excellent thermal and oxidation stability, and long service life. GTL oils, synthesized from natural gas, are also gaining importance thanks to their outstanding lubricant properties.

Technical and Economic Drivers

The demand for high-performance base oils continues to rise: Modern engines and industrial machinery require lubricants that reduce emissions, extend maintenance intervals, and protect components reliably. At the same time, economic production processes remain essential. Refineries therefore adjust their operations to flexibly produce high-quality base oils alongside other marketable products.

API Classification: Understanding Quality Levels

To distinguish between different base oil qualities, the American Petroleum Institute (API) has established five groups. Each group represents a specific refining level and quality standard. The higher the group number, the greater the processing effort and base oil quality.

API Group I – Solvent Refining
The simplest category of base oils, produced through solvent extraction. These oils contain varying hydrocarbon structures and are mainly used in less demanding applications.

 

Industrial Lubricants: Versatile Solutions for Stationary Equipment and Special Applications

The term industrial lubricants covers both liquid and solid lubricants, primarily designed for use in stationary machines and production facilities. Unlike automotive lubricants, which are developed for use in vehicles, industrial lubricants are tailored to meet the requirements of industrial manufacturing and processing operations. Special applications, such as in marine engines, railway systems, or stationary gas engines, also rely on specific industrial lubricants.

To provide a better overview, industrial lubricants are categorized into product groups according to their specific use and technical properties. The main groups include:

Hydraulic oils
Gear oils
Circulating oils and machine oils
Slideway oils
Paper machine oils
Bearing lubricating oils
Metalworking oils
Quenching oils
Coolants and cutting fluids
Rolling oils
Corrosion protection oils
Electrical insulating oils and transformer oils
Compressor oils
Refrigeration compressor oils
Turbine oils

In addition, there are industrial oils that are not primarily used for lubrication but serve other functions, such as:

Mould release oils
Separation oils
Heat treatment oils
Heat transfer oils

Lubricating greases are also classified as industrial lubricants in a broader sense.

The requirements for these lubricants are typically defined by the specific technical conditions of the respective equipment. National and international standards ensure consistent quality and reliable performance across all product groups.

For almost every product type, different performance classes are available to suit varying operational conditions.

An important selection criterion for liquid industrial lubricants is their viscosity, classified into standardized viscosity grades as per the ISO 3448:1992 standard (available in German translation as well). The classification is based on kinematic viscosity, measured according to ISO 3104. In total, 18 viscosity ranges are defined, centered around a midpoint viscosity at 40 °C, allowing a tolerance of ±10% within each ISO VG class.

 

Hydraulic Oils: High-Performance Fluids for Power Transmission and Lubrication

Hydraulic oils are specialized fluids used in hydraulic systems for power transmission. Unlike pneumatic systems, which rely on air, hydraulic systems use pressurized fluids to generate force. These systems are widely used in industry, machinery, construction equipment, marine applications, and aircraft.

Depending on the medium used, two primary types are distinguished:

  • Water-based hydraulic systems: utilize water with emulsified oil to ensure corrosion protection and lubrication.

  • Oil-based hydraulic systems: employ hydraulic oils that also perform lubrication, cooling, sealing, and cleaning functions.

Two different power transmission principles apply:

  • Hydrostatic systems: use pressurized fluid to directly move cylinders or hydraulic motors.

  • Hydrodynamic systems: convert the fluid’s movement into rotational force via turbines.

While transferring force through fluid may seem simple, modern hydraulic systems impose strict requirements on hydraulic oils. These fluids must protect numerous components, ensure stable flow properties, resist aging, and maintain high cleanliness standards. Therefore, hydraulic oils are highly advanced technical products.

Standards and Classifications

International and national standards define the technical minimum requirements for hydraulic oils, including performance criteria and testing methods:

  • DIN 51524 Parts 1–3: specifying HL, HLP, and HVLP hydraulic oils

  • ISO 15380: for environmentally acceptable hydraulic fluids

  • ISO 12922 / CEN/TR 14489: for fire-resistant hydraulic fluids

Depending on the application, hydraulic oils must meet specific requirements regarding water separation, oxidation stability, wear protection, and filterability.

Specialized Hydraulic Fluids

Fire-resistant hydraulic fluids are used in high-temperature environments where leaks could pose a fire hazard. They are divided into four types:

  • HFA: Oil-in-water emulsion (water content > 80%)

  • HFB: Water-in-oil emulsion (water content > 40%)

  • HFC: Water-glycol solutions (water content > 35%)

  • HFD: Water-free synthetic fluids

Environmentally acceptable hydraulic fluids, used in ecologically sensitive areas, are classified under ISO 15380 and categorized as:

  • HETG: Based on triglycerides (vegetable oils)

  • HEPG: Based on polyglycols

  • HEES: Based on synthetic esters

  • HEPR: Based on synthetic fluids such as polyalphaolefins

Quality and Cleanliness: Key to System Protection

Most equipment manufacturers require hydraulic oils conforming to DIN 51524 Part 2 (HLP) or Part 3 (HVLP). Key quality criteria include:

  • High oxidation stability and aging resistance

  • Excellent water separation

  • Low foaming tendency

  • Good filterability

  • Seal compatibility

Oil cleanliness is also critical. Hydraulic systems must be filled using dedicated filters to remove fine particles that could accelerate wear and reduce service life. DIN 51524 references cleanliness class 21/19/16, but actual requirements should be defined based on specific system needs.

Using high-quality hydraulic oils ensures reliable operation, extended maintenance intervals, and optimum protection for your hydraulic system.

 

Gear Oils: High-Performance Lubricants for Industry and Automotive Applications

Gear oils are specialized lubricants used in both stationary industrial equipment and vehicle transmissions. They ensure reliable power transmission and protect mechanical components by providing consistent lubrication under various operating conditions.

Two primary types of gear oils are distinguished:

  • Industrial gear oils for machines and stationary systems

  • Automotive gear oils for vehicles of all types

In sectors like marine, railway, or stationary gas engines, industrial gear oils are generally used due to their similarity to stationary gearbox requirements.

Industrial Gear Oils: For Demanding Drives and Gears

Industrial gearboxes come in many designs: helical, bevel, planetary, worm, hypoid, and plain bearing gear units. They must function reliably under high loads, temperature variations, and fluctuating operating conditions.

Lubrication methods:

  • Splash lubrication (oil bath) in smaller and mid-sized gearboxes

  • Circulating oil lubrication in large or high-speed units

Key requirements for industrial gear oils:

  • Rebuilding the lubricant film with every gear mesh

  • Managing varying sliding speeds and high surface pressures

  • Reducing mixed friction through optimized viscosity and additive formulation

  • Ensuring effective heat dissipation to avoid overheating and oil degradation

Standards like DIN 51517 define minimum quality criteria. ISO VG viscosity grades specify oil thickness, while additional manufacturer approvals often apply.

Critical factors for service life:

  • Monitoring oil temperature

  • Maintaining correct oil levels

  • Filtering to ensure oil cleanliness

  • Conducting regular used oil analysis

Automotive Gear Oils: For Manual, Automatic, and Axle Transmissions

Vehicles use various gear systems:

  • Manual transmissions (including dual-clutch gearboxes)

  • Automatic transmissions (planetary gear systems)

  • Axle drives / hypoid gears

  • Transfer cases and reduction gearboxes

Automotive gear oils are mainly classified according to API standards, where:

  • GL stands for Gear Lubricant

  • The number (e.g. GL-4, GL-5) indicates performance level

Automatic Transmission Fluids (ATFs) serve both as lubricants and hydraulic fluids. Specifications like Dexron (GM), Mercon (Ford), or ZF define exact requirements. Only officially approved oils should be used, as modern transmissions operate under high loads and temperatures.

Viscosity by SAE grades:
SAE standards categorize gear oils by viscosity:

  • Single-grade oils (e.g. SAE 90)

  • Multigrade oils (e.g. SAE 75W-90)

Modern vehicles increasingly rely on lower-viscosity oils to minimize energy losses and improve fuel efficiency.

 

Engine Oils: Why Filtration Systems Cannot Replace Oil Changes

Products promising to extend or even eliminate oil change intervals by using advanced filters or additive boosters appear on the market repeatedly. However, from a technical standpoint, such solutions are unreliable and should be approached with caution: Engine oil ages due to complex chemical reactions, not simply because of dirt particles. Neither filtration nor additive replenishment can reliably stop this process.

Why Oil Degradation is Inevitable

Engine oils are hydrocarbon-based fluids exposed to heat, oxygen, nitrogen compounds, and metal catalysts during operation. This triggers the formation of highly reactive molecules called radicals, which link together to form long polymer chains. These polymers thicken the oil and eventually precipitate as sludge. Antioxidants and other additives slow this process but cannot prevent it entirely.

While filtration can remove some polymers, radicals remain in the oil and accelerate the degradation chain reaction. Once initiated, this process quickly renders the oil unusable.

Additionally, oil degradation generates acids, which lower the oil’s pH and promote corrosion – and acids cannot be filtered out.

Why Additive Replenishment Fails

Replenishing additives also fails for several reasons:

  • Additives deplete at varying rates

  • Interactions between additives are unpredictable

  • Required additive quantities would increase exponentially

  • Wear protection additives bond chemically to metal surfaces and cannot be replenished effectively

Biofuels worsen the problem: Biodiesel, for example, can mix with engine oil and doesn’t fully evaporate at standard oil temperatures. No filtration method can remove these liquid contaminants.

Moreover, over time, volatile oil components evaporate, increasing oil viscosity and fuel consumption – again, something filtration cannot prevent.

Conclusion: Oil Changes Remain Essential

Scientific research – including studies commissioned by the German Federal Environment Ministry – confirms:
Bypass filtration systems and additive boosters cannot replace regular oil changes.

Following manufacturer-recommended oil change intervals remains the only way to ensure engine protection and long-term performance.

 

Lubricating Greases: Structure, Properties, and Selection Criteria

Lubricating greases are semi-solid or solid lubricants composed of a base oil thickened by a gelling agent (thickener). The thickener functions like a sponge, retaining the oil under static conditions and releasing it gradually when mechanical load is applied. This ensures continuous lubrication, even in areas where liquid lubricants are unsuitable.

Consistency is determined by the type and amount of thickener used. Classification follows the internationally recognized NLGI consistency classes, based on worked penetration according to DIN ISO 2137, also described in DIN 51818.

Types of Thickeners and Their Effects

Different thickeners are used in grease production:

  • Metal soaps (e.g. lithium, calcium, or sodium soaps)

  • Complex soaps (e.g. lithium, calcium, sodium, or aluminum complexes)

  • Non-soap thickeners (e.g. bentonite, polyurea)

The thickener type mainly determines the grease’s operating temperature range. Complex greases and non-soap-based gel greases typically withstand higher temperatures than simple metal soap greases.

Greases are further classified by their base oil type:

  • Mineral oil-based greases

  • Synthetic oil-based greases

Standardized Labelling According to DIN 51502

To ensure clear identification, lubricating greases are labeled according to the DIN 51502 standard. This code provides detailed information on:

  • Grease type and application area

  • Mineral or synthetic base (symbol)

  • Consistency class (NLGI)

  • Upper and lower operating temperatures

  • Water resistance

This labelling system allows precise selection of the right grease for the intended application.

Functional Advantages of Lubricating Greases

In addition to providing wear protection, friction reduction, and corrosion prevention, greases perform specific additional functions:

  • Sealing against air, water, and contaminants

  • Preventing leaks in moving components

  • Avoiding lubricant loss

Therefore, greases are especially suitable for applications requiring long-term lubrication without relubrication, or where oils cannot be effectively retained.

Important: When switching greases, the compatibility between the existing and the new grease should always be checked. Mixing incompatible thickeners can impair consistency, dropping point, and overall lubrication performance.

Choosing the correct grease is crucial for lubricant durability and the service life of mechanical systems.

 

Cooling Lubricants (KSS): Cooling, Lubricating, Protecting

Cooling lubricants (KSS) are specialized fluids essential in metal cutting and forming processes. They serve two primary functions:

  • Cooling: Removing heat from the process

  • Lubricating: Reducing friction and tool wear

In addition, KSS provide corrosion protection and help flush away chips and debris.

Types of Cooling Lubricants

Two main categories are distinguished:

  • Non-water-miscible KSS
    Based on mineral oils or synthetic hydrocarbons
    ✔ Excellent corrosion protection
    ✔ Long service life
    ✔ High lubricity
    ✘ Limited cooling capacity
    ✘ Higher purchase and disposal costs

  • Water-miscible KSS
    Composed of concentrate (approx. 5%) mixed with water (approx. 95%)
    ✔ Excellent cooling and flushing properties
    ✔ Lower costs
    ✘ Susceptible to microbial growth and corrosion
    ✘ Requires careful maintenance

All variants are defined in DIN 51385.

Why KSS Are Indispensable

Dry machining or minimum quantity lubrication (MQL) are not universally applicable. Particularly when working with hard-to-machine materials, cooling lubricants remain essential to ensure tool life and dimensional accuracy.

Cooling lubricants account for up to 16% of production costs – exceeding even tool costs – highlighting their economic importance.

KSS: An Integral Process Component

KSS significantly influence:

  • Tool wear

  • Workpiece quality

  • Machine uptime

  • Occupational health and safety

Their selection and maintenance are regulated by standards and guidelines:

  • VDI 3035: Design of machine tools for KSS use

  • VDI 3397 Parts 1–4: Selection, care, disposal, microbiology

  • DGUV-R 109-003: Occupational safety in KSS handling

Boric Acid in KSS: Controversy and Regulation

Due to updated EU classifications, boric acid and borates are now deemed “reproductive toxicants category 1B.” For cooling lubricants:

  • KSS with 5.5% or more free boric acid must be labeled accordingly

  • Most KSS concentrates on the market fall well below this threshold

Accurate boric acid quantification is performed using 11B-NMR spectroscopy. Studies show that over 98% of KSS products are not subject to labeling requirements.

While boric acid remains a common corrosion inhibitor in water-miscible KSS, its future use may be restricted through inclusion in the REACH Annex XIV.

Conclusion: Proper Selection and Maintenance Are Critical

Cooling lubricants are more than consumables – they are vital tools within the manufacturing process. Selecting the right KSS, combined with proper maintenance and disposal, ensures high product quality, machine protection, and compliance with occupational health standards.

 

Rolling Oils and Rolling Emulsions: Lubricants for Optimal Surfaces and High Productivity

Rolling oils and rolling emulsions are specialized lubricants used in hot and cold rolling of metals. They control friction between strip and roll, minimize wear, and ensure excellent surface quality of the final product. At the same time, they support heat management in the rolling process.

Rolling Processes and Lubricant Requirements

Regardless of the metal (steel, aluminium, copper, stainless steel), the rolling process is similar: Metal strip is passed between rotating rolls and reduced to the desired thickness. Without suitable lubrication, high friction would lead to surface defects, roll wear, and increased energy consumption. Rolling fluids serve to:

  • Control friction reduction

  • Cool rolls and strip

  • Remove particles from the roll gap

  • Prevent roll coating (metal particle transfer to rolls)

The choice of lubricant depends on:

  • Metal type

  • Rolling speed and temperature

  • Reduction per pass

  • Roll stand type (duo, quarto, sexto, multi-roll)

Hot Rolling: Use of Rolling Emulsions

In hot rolling, metals are heated to between 500 °C (aluminium) and over 1000 °C (steel). As oils would combust at such temperatures, rolling emulsions are used – water-based coolants with a small oil content. Their functions include:

  • Intensive cooling of hot metal

  • Effective flushing action

  • Controlled friction management

  • Corrosion protection

Rolling emulsions are supplied as concentrates and diluted with water at the user site. Oil content typically ranges from 0.5 to 6%.

Cold Rolling: Use of Rolling Oils

In cold rolling, metals are processed at room temperature. Rolling oils are mainly used, occasionally emulsions. Requirements for rolling oils include:

  • Defined friction levels for process control

  • Excellent surface finish

  • High thermal stability

  • Low foaming and residue formation

  • Efficient water separation

Rolling oils are formulated from highly refined base oils, combined with additives like antioxidants, friction modifiers, anti-wear, and corrosion inhibitors. Viscosity is customized to the specific rolling process.

Comparison: Rolling Emulsions vs. Rolling Oils

Rolling Emulsions Rolling Oils
Excellent cooling Best surface quality
Low fire risk Longer service life
High reductions possible Lower maintenance effort
Requires monitoring Higher fire risk
Shorter lifetime Lower reduction ratios

Special Lubricants: Low-Stain Oils

Walz plants also use hydraulic, gear, and circulation oils. If these oils contaminate the rolling oil, they can cause staining during annealing. Special low-stain oils prevent this by evaporating almost residue-free during annealing. They are ideal for aluminium foil and food packaging applications. However, they may not meet all conventional industrial oil standards due to their specialized formulation.

 

Food Grade Lubricants & H-Classes: Ensuring Safety in Production

Food grade lubricants (H1) are formulated for incidental contact with food and meet stringent HACCP and FDA (21 CFR 178.3570) standards to ensure food safety.

H-Class Definitions

  • H1: For incidental food contact; FDA-compliant and HACCP-safe.

  • H2: For enclosed non-food contact applications—not food-grade.

  • H3: Corrosion-resistance oils for tools—must be wiped off before contact.

  • 3H: Release agents allowed in certain food applications (see FDA 21 CFR 172.878).

  • NSF/InS: International registers that list approved H1 lubricants.

  • ISO 21469: Hygiene standard for H1 lubricant manufacturers.

  • ISO 22000: Management standard for food producers, not lubricant vendors.

  • EHEDG Doc 23: Best practices for hygienic lubricant use in food production.

Why Using H1 Lubricants Makes Sense

  1. Food Safety & HACCP Compliance
    H1 oils meet FDA/HACCP requirements and are safe for use in food-adjacent areas.

  2. Uniform Certification
    ISO 21469 certification ensures hygiene across production and supply chains.

  3. Minimized Errors
    Color and number coding help avoid the use of incorrect lubricants.

  4. Process Reliability
    Using H1 oils throughout reduces substitution risk and simplifies management.

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