Discover our range of oils online at Cromwell.co.uk. We stock a wide range of oils for use in hydraulic systems, lubricating components and more. Choose just what you need, from aerosol sprays, jerry cans and bottles from reliable brands, like Mobil®, Castrol® and Swarfega®.

What are oils?

Hydraulic oils are non-compressible fluids which are comprised of a mix of liquids including mineral oil, silicone and glycol. They contain additives according to their required application, like rust-resistance for lubrication.

When are oils used?

Hydraulic oil or fluid has a multitude of uses for hydraulic machinery and equipment. Its main use is to conduct power within machinery but is also widely used for lubricating machine components as well as sealing and cooling equipment.

Oil types

A combination of base-oil and additives, there are three types of hydraulic oils.

Synthetic   -   The most energy efficient of hydraulic oils, synthetic oils are based on Esters, (made via a reaction when alcohol and fatty acids are combined).

Mineral based   -   Solvent refined mineral oil is derived from crude oil

Vegetable oil-based   -   Plant-based raw materials make this oil, which has excellent eco-credentials, but is not currently produced en masse due to the limitations in its technical characteristics

Considerations when choosing oils

Additives - the additives included in an oil are designed to enhance their properties for use. For example, thermal stability allows an oil to be used with certain operating temperatures without risk.

Base oil - synthetic oils produce lower CO2 emissions and reduce energy consumption for an efficient energy solution. The practical alternative is mineral-based oils, which are less energy efficient.

Viscosity - Choose the right viscosity grade according to the operating temperatures of your machinery to ensure the best performance.

Application - supplied in a range of packaging, choose between bottles, aerosol sprays and canisters to deliver the oil in the method you require.

Oil jargon buster

To help you shop with confidence, we've outlined a quality standard associated with petrol and oil-related products to help you make the best purchase.

Want does quality standard ISO 4263-1:2003 mean?

This standard outlines the test guidance on petrol and other related products to ensure the ageing behaviour of these fluids performs according to European standards. Ageing behaviour in this instance covers the corrosive resistance of mineral oils used in hydraulic and turbine systems and as circulating oils.

Let's break it down...

• ISO - The International Organization for Standardization is the international regulatory body that ensure that products adhere to international quality and safety standards

• 4263 - This is the legislation number for this document

• 1 - This is the part of the document relative to mineral oils

• 2003 - This is the year that this legislation was published. It was reviewed and confirmed in 2020 and remains current


How does hydraulic oil work?

The non-compressible properties of hydraulic oil are used to drive the oil through hydraulic machinery using a pump or piston. The pressure build-up created by the oil facilitates movement at the end of the machinery

What does VG stand for on hydraulic oil?

This is the International Organization for Standardization's viscosity grade and defines each category of graded oil according to its viscosity (how easy the oil is to pour at specified temperatures).