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High Viscosity Index (HVI) Hydraulic Oil | Free Shipping | High Viscosity Index (HVI) hydraulic oils that will maintain their ideal viscosity (or thickness) over an extreme range of temperatures.

HVI Hydraulic Oils achieve increased performance levels through the use of highly refined base oils which have less wax / paraffin content. They may also be enhanced by the addition of Viscosity Index Improvers; these additives change form and size to counteract the fluids natural tendency to thinning and thickening due to temperature change.

High viscosity oils are also commonly used in electrical service bucket trucks due to their high dielectric strength which means they do not carry an electrical current.

Viscosity index (VI) is an arbitrary measure for the change of viscosity with variations in temperature. The lower the VI, the greater the change of viscosity of the oil with temperature and vice versa. It is used to characterize viscosity changes with relation to temperature in lubricating oil.

The viscosity of liquids decreases as temperature increases. The viscosity of a lubricant is closely related to its ability to reduce friction. Generally, the least viscous lubricant which still forces the two moving surfaces apart is desired. If the lubricant is too viscous, it will require a large amount of energy to move (as in honey); if it is too thin, the surfaces will come in contact and friction will increase.

Many lubricant applications require the lubricant to perform across a wide range of conditions, for example, automotive lubricants are required to reduce friction between engine components when the engine is started from cold (relative to the engine's operating temperatures) up to 200 °C or 392 °F when it is running. The best oils with the highest VI will remain stable and not vary much in viscosity over the temperature range. This allows for consistent engine performance within the normal working conditions.

The VI scale was set up by the Society of Automotive Engineers (SAE). The temperatures chosen arbitrarily for reference are 100 and 210 °F (38 and 99 °C). The original scale only stretched between VI=0 (lowest VI oil, naphthenic) and VI=100 (best oil, paraffinnic) but since the conception of the scale better oils have also been produced, leading to VIs greater than 100 (see below).

Viscosity Index Classification
..35 Low
35..80 Medium
80..110 High
110.. Very High