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What makes up a lubricant?

The bulk of a lubricant is the base oil, which can be vegetable, mineral, or synthetic in nature.

Vegetable-based lubricants can offer various advantages, such as biodegradability and lower toxicity, but higher production costs limit their competitiveness. Mineral and synthetic oils are generally more common in industrial settings.

Mineral oil is refined to varying levels and graded by quality. It comprises four compounds, each with their own applications, namely paraffin, branched paraffin, naphthene, and aromatic. The paraffinic oils, for example, have a long, chained straight structure that makes them suitable for industrial lubricants and engine oils. Synthetic oils have a similar straight structure, but unlike with mineral oils, the molecular size and weight does not vary, making its behaviour more predictable.

With synthetic oil being so consistent, you may wonder why mineral oil is used at all. In many applications, a good quality mineral oil (based on paraffinic oils) may perform just as well as a synthetic but at a lower cost and with fewer issues (e.g. toxicity, compatibility, disposal). On the flip side, more demanding applications may require the extra qualities that only a synthetic oil can provide.

Viscosity, which is the resistance to shear and flow, is the first aspect to look at when choosing a lubricant. Basically speaking, the higher the viscosity, the slower something flows, and different applications prefer various viscosities. For example, transmission oil has a higher viscosity than motor oil.

The next aspect is the viscosity index (VI), which determines how the viscosity changes with temperature. For example, Mobile DTE Oil Heavy Medium has a high VI of 107 to ensure minimum variation in film thickness.

Other additives are added for various purposes. One prevents rust by coating metal surfaces with a water-repellent film. Another additive limits abrasion by catching loose particles and allowing them to be filtered out. Yet another additive can react with surfaces and prevent metal-to-metal contact by forming a protective film, which is especially useful in high pressure applications. Defoamants may also be added to minimise foaming, while detergents may work to clean surfaces and neutralise acids.

Finally, if a thickener is added to the base oil and additive mix, the lubricant becomes a grease, which can be more suitable in some applications.

As you can see, there are a number of factors to consider when choosing the best lubricant, but learning more about proper lubrication regimes can help you achieve the cost savings, reliability, longer machine life, and improved efficiency that every industrial company desires.

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