What Factors Affect Hydraulic Oil Viscosity?

Malcolm Tatum

Hydraulic oil viscosity is an important factor in how well a particular oil is suited for use in certain types of engines or other types of machinery. In order to provide the highest level of performance, the oil must be able to withstand the stress or tension when the machinery is in operation. There are several factors that can have an impact on hydraulic oil viscosity, including temperature and the composition of the oil itself.

Woman holding a book
Woman holding a book

Temperature is one of the main factors that can have some sort of effect on hydraulic oil viscosity. As the machinery begins to heat during operation, a thicker oil product will be made that then begins to thin somewhat. The goal when choosing the right hydraulic oil is to identify a grade and type that will only thin enough to provide the right level of protection for the motor, and not become so thin that the product fails to coat the working components and allows friction to begin wearing the machine parts. Different types of hydraulic oil are graded based on the ability to retain a certain level of viscosity when exposed to specific levels of temperature.

Another factor that can affect hydraulic oil viscosity is the actual composition of the oil itself. This has to do with not only the ingredients and additives that are part of the product, but also the amount of each ingredient introduced into the mix. There are a number of different types of hydraulic oils, with each one using a different combination of ingredients. For example, mineral hydraulic oil uses a petroleum base while synthetic types may use polyol ester, phosphate ester, or water glycol as the core ingredient. Some blends will also include additives that are designed to enhance the ability of the product to remain thicker during actual use, even at very high temperatures.

For end users, identifying hydraulic oil viscosity involves making use of an industry standard known as a viscosity index. This index helps to provide information on how different types of engine oils perform under certain circumstance. The viscosity levels can be related to the lubricant recommendations provided by the manufacture of the machinery, making it easier to identify which type of hydraulic oil would provide maximum protection for the motor components. Making use of the index can help prevent the purchase of an oil that will not hold up to the temperature generated within the motor, and ultimately aid in minimizing the wear and tear that comes with ongoing operation of the equipment.

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