Lubricants and Industrial Oils: Answers to 7 Most Common Questions from Technicians and Maintenance Staff

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Lubricants and industrial oils play a key role in the trouble-free operation of machinery and equipment. However, technicians and maintenance staff often encounter questions that lack clear answers—whether it concerns selecting the right type of lubricant, interpreting changes in its properties, or optimizing replacement intervals. In this article, we focus on the seven most common queries we address with our customers from production facilities. We will uncover what lies behind common issues such as foaming, color changes, or loss of viscosity, and provide advice on how to prevent or effectively resolve them.

1. How to choose the right lubricant for a specific application?

Selecting the right lubricant depends on several key factors that need to be considered at the initial stage. The first step is analyzing the operating conditions: temperature, pressure, movement speed, and the environment in which the lubricant will operate. For example, high temperatures require lubricants with high thermal stability, such as synthetic oils or special greases with anti-oxidation additives. Conversely, in cold environments, low-temperature fluidity is important to ensure the lubricant does not lose its properties.

Another criterion is the type of friction—whether it is sliding, rolling, or combined. For rolling bearings, plastic lubricants with consistency adapted to the rotational speed are often used, while for sliding bearings, liquid oils with extreme pressure additives are more suitable. It is also important to consider compatibility with materials, especially for seals and plastic components. It is always recommended to consult the manufacturer's technical data sheet and, in case of uncertainty, conduct a trial operation with monitoring of the lubricant's condition.

2. How often should industrial oils be changed, and how can you tell it's time for a replacement?

The replacement interval for industrial oils is not universal and depends on the type of oil, operating conditions, and equipment manufacturer requirements. For conventional mineral oils, replacement is recommended after 2,000 to 4,000 operating hours, while synthetic oils can last up to 8,000 hours or longer. However, the key factor is the condition of the oil, which can be monitored through regular analyses. Laboratory tests can detect the presence of metal particles, oxidation, additive depletion, or contamination by water or impurities.

Visual inspection can provide the first clues – cloudy or dark oil often signals degradation. Modern equipment often features sensors for monitoring viscosity, conductivity, or particles, which automatically alert you when an oil change is needed. Ignoring these signals can lead to machine damage, increased energy consumption, and costly repairs. Regular maintenance and oil analyses thus represent an investment in the long-term reliability of your equipment.

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3. What are the key differences between mineral, synthetic, and semi-synthetic oils?

Mineral oils are refined from petroleum and represent the most common and economically advantageous option. Their advantages include good lubricity and wide availability, but they have limited resistance to high temperatures and oxidation. This means they degrade more quickly and require more frequent changes. They are suitable for standard applications with mild operating conditions where extreme stability is not required.

Synthetic oils are produced through chemical synthesis and offer excellent performance properties: higher temperature stability, better low-temperature fluidity, and resistance to oxidation. As a result, they extend equipment lifespan and reduce energy consumption. Their disadvantage is the higher purchase price, which, however, can be worthwhile in demanding applications such as high-speed machines or extreme temperature conditions. Semi-synthetic oils combine the advantages of both types—they provide better performance than mineral oils at a more affordable price than fully synthetic variants.

4. How to store lubricants and oils correctly to preserve their properties?

Proper storage of lubricants and oils is crucial for maintaining their quality and performance. The basic rule is to store them in a dry, cool, and well-ventilated environment, ideally at temperatures between 10 and 25 °C. Extreme temperatures can cause additive degradation or separation of components, especially in greases. Containers with lubricants should be sealed and protected from direct sunlight, which accelerates oxidation.

It is also important to follow the "first in, first out" (FIFO) principle to avoid long-term storage of older batches. Before use, it is advisable to gently mix the containers, especially with greases, where separation of the thickener and oil may occur. Contamination with water, dust, or other substances can significantly reduce the lubricant's effectiveness, so it is essential to ensure the cleanliness of storage areas and handling tools. By adhering to these principles, lubricants will retain their properties throughout the shelf life indicated on the packaging.

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5. Why is lubricant viscosity important and how to choose it correctly?

Viscosity is a fundamental parameter of a lubricant that determines its ability to form a protective film between friction surfaces. Too low viscosity leads to insufficient surface separation, increased wear, and the risk of seizure. Conversely, too high viscosity increases internal friction, impairs cooling, and raises energy losses. The correct choice of viscosity depends on operating conditions: temperature, load, speed of movement, and type of machinery.

For selection, we follow the equipment manufacturer's recommendations and standards such as ISO VG (viscosity grades). For example, hydraulic systems commonly use oils with a viscosity of 32–68 mm²/s at 40 °C, while high-speed bearings are better suited to lower viscosities (10–32 mm²/s). At extreme temperatures, the viscosity index must be considered – synthetic oils maintain stable viscosity even under temperature fluctuations, unlike mineral oils. Always verify that the lubricant meets the requirements for the operating temperature range.

6. Which additives improve the properties of industrial oils and when should they be used?

Additives are key to extending the functionality of base oils and adapting their properties to specific applications. The most common include antioxidants, which slow oil aging and extend its service life, especially at high temperatures. Anti-wear additives (e.g., zinc or phosphorus compounds) protect friction surfaces from wear under boundary lubrication conditions. Corrosion inhibitors prevent damage to metal components caused by moisture or acidic degradation products.

In extreme conditions, such as high pressures or low speeds, EP (extreme pressure) additives are used to prevent micro-seizure. For applications with variable temperatures, viscosity index improver additives are important. It is crucial to follow the recommended dosage – excessive amounts of additives can lead to deposit formation or negatively affect other oil properties. When selecting additives, always consider compatibility with machine materials and other lubricant components.

7. How to Address Lubricant Contamination and How to Prevent It?

Lubricant contamination is one of the main causes of premature machine failure. The most common contaminants are solid particles (dust, metal wear particles), water, air, and chemical impurities (e.g., fuels or coolants). Solid particles cause abrasive wear, while water accelerates oil oxidation and promotes corrosion. Air in the oil leads to foaming and impaired lubrication, which can cause cavitation in hydraulic systems.

Prevention involves regular maintenance of filtration systems, machine sealing, and proper lubricant storage. To remove solid particles, filters with appropriate fineness (e.g., 3–10 microns for hydraulic systems) are used. Water can be removed using separators or vacuum dehydrators. Regular oil analysis (e.g., determining water content, particle count, or spectrometric analysis of metals) enables early contamination detection and extends the lifespan of both the lubricant and the machine. Always follow procedures according to the manufacturer’s instructions and applicable safety regulations.

Do you have specific lubricant requirements?

Every application requires an individual approach. GCG Group provides detailed technical data sheets and safety data sheets (SDS) for all supplied lubricants and oils in accordance with REACH and CLP regulations. Our experts will be happy to advise you on selecting the right product or optimising the maintenance of your machinery. Contact us – or browse our catalogue of over 1,300 products right away.