What is the Most Important Property of a Lubricant?

While there are many different characteristics considered when choosing a lubricant, viscosity is considered the most important. Below, we take a look at why viscosity is often prioritised when assessing products and deciding what is the most important property of a lubricant.

What is viscosity?

Viscosity is a parameter used to measure a lubricant’s internal resistance to flow. In simpler terms, it describes how thick or thin a lubricant is. This characteristic is important as it determines how a lubricant performs when in circulation and if it’s suitable for a particular application.

Why viscosity matters

Viscosity is often the most important characteristic considered when assessing the suitability of a lubricant, with some of the most important reasons outlined below:

• Ability to reduce friction

Reducing friction is a core goal of lubricants and viscosity has a big impact on performance. The thickness of a lubricant determines the strength and longevity of the protective film created between moving parts. This is ultimately what prevents metal-on-metal contact and minimises friction.

• Load-carrying capacity

Viscosity can affect load-carrying capacity, i.e. the maximum level of stress an operating system can be placed under without compromising function. By forming a protective layer between moving parts, lubricants increase load-carrying capacity and prevent unplanned downtime.

• Heat generation

Along with other goals, lubricants are often used to reduce heat generation in gears, cylinders, bearings and other moving parts. Viscosity can affect a lubricant’s ability to reduce heat and maintain an ideal operating temperature, making it one of the most important properties considered when selecting a product.  

• Efficiency

The thickness of a lubricant and its internal resistance to flow can affect how efficiently a machine runs. For example, an oil lubricant that’s too thin may not form a protective film capable of preventing friction between moving parts. This could increase the operating temperature of the machine, accelerate wear and release contaminating particles into the system. Similarly, if an oil is too thick it could create unnecessary resistance and force the machine to work harder. This could result in an increase in energy consumption and generate excess heat.

A rounded approach to lubricant analysis

What is the most important property of a lubricant? While viscosity is often crowned the most important for the reasons listed above, the reality is that all properties contribute to the overall quality, suitability and performance of a lubricant. Find out more about some of the other key characteristics of lubricants, including flash point, pour point and thermal stability in ‘What Are the Chemical & Physical Properties of Lubricants’.