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Hydraulic Oil

Hydraulic oil explained

Hydraulic oils, or hydraulic fluids as they are often referred to, transfer power and energy through hydraulic systems. As well as this transfer of power, they act as a coolant, lubricant and sealant, and are crucial to the performance of machinery and equipment used across a range of industries and sectors.

What is hydraulic oil?

Hydraulic oil is principally a combination of a mineral based oil and man made additives. There are synthetic hydraulic oils available, but using a fully synthetic and can be safely used in very high temperatures. This is particularly beneficial for commercial and industrial settings where hydraulic systems can be expected to operate at extreme temperatures.

Added to this base mineral oil are several other ingredients including esters, ethers, silicone and various chemical compounds. Additives are then mixed in during the production process. The additives will vary according to the intended final use of the hydraulic oil, with different blends producing different results. The most common additives found in hydraulic oils are anti-wear, antifreeze, anti-corrosion and anti-foaming additives, all vital for the sustained performance of hydraulic operating systems. 

Hydraulic oil uses

There are a huge number of applications and industries that use hydraulic oils. Below you’ll find some of the more common examples, but nearly all industries will use hydraulic operating systems and oils in some capacity.


The construction industry uses hydraulic oils extensively for machinery and vehicles like cranes, excavators and tip trucks


Log splitters, tractors and snow ploughs are integral to the smooth running of farms and agricultural businesses, performing high intensity tasks


Hydraulic oil specifically designed for the aviation industry is used across aircraft controls, hangar doors and aircraft jacks


The lifting mechanism of a fork lift truck comes under considerable pressure moving heavy goods and pallets


Independent workshops require the use of car jacks and automotive lifts which need a high viscosity oil to handle a vehicle’s weight

Viscosity, flash points and grades

As hydraulic oils operate across many types of machinery, their properties and molecular structure will vary. Hydraulic oils on the whole, have a high viscosity rating. This is due to the above average temperatures hydraulic systems often operate in. When exposed to high temperatures oil can flow too rapidly, leading to leaks or impairment of the oil’s properties. Resisting these high temperatures is a crucial function of hydraulic oil. Viscosity improvers will be added to the oil as per the specific requirements of the machinery or equipment. The wrong viscosity rating could lead to damage or reduced performance, which is why hydraulic oils are not one-size-fits-all and must be tailored to their end use.

Viscosity Index Table

Further to the understanding of viscosity ratings, all hydraulic oils will also have a flash point, the lowest temperature at which the oil will combust. Choosing an oil with a high flash point, will mean it can withstand higher temperatures. For certain industries, ensuring the oil has a high flash point is vital and should be discussed before choosing the right hydraulic oil.

To help businesses choose the correct oil, hydraulic fluids are given a grade. In the UK, hydraulic oil is usually graded by the International Standards Organisation (ISO), which is why oil grades often begin with an ISO prefix. Other grades are AGMA (American Gear Manufacturers Association) or SAE (Society of Automotive Engineers). These grades pertain to the  viscosity of the oil; for example, ISO VG 68 Hydraulic Fluid shows the viscosity rating as 68 out of 100, indicating it is a medium viscosity oil. ISO VG 68 is typically used for load bearing applications. 

Checking you have the right grade of hydraulic oil is essential. Certas Lubricant Solutions offers complete support and technical advice to ensure you get the absolute best product for your business. 

Benefits of hydraulic oil

The benefits of hydraulic oil are vast. Although primarily they transfer power, their additional functions are varied and many, and often work alongside other lubricants for optimum performance and results.

Non compressible – withstanding significant pressure hence their use in heavy duty machinery and vehicles

Non corrosive – less likely to cause wear or damage to the system

Fire resistant – can be used in temperatures well above 100 degrees and remain thermally stable in a range of temperatures

Anti foaming – hydraulic oil is far less likely to cavitate and thus has a prolonged shelf life.

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Biodegradable options

The majority of hydraulic oils use a base mineral oil. However, as industries move further towards net zero, several oils are now created using biodegradable and natural alternatives like rapeseed or canola oil. This is particularly beneficial to industries where an oil spill could be especially harmful, such as marine or agriculture

Making the right choice

Choosing the right hydraulic oil means getting the maximum from your machinery and equipment and boosting your business output. Our expert team can offer full technical and advice and support, pointing you in the right direction for your specific needs.

  • Heavy loads
  • All weathers
  • High pressure
  • Stabilising
  • Environmentally friendly

We are partnered with premium manufacturers like Shell, Castrol, Q8 Oils and Valvoline and can recommend a hydraulic oil with all the benefits you need for a competitive edge.

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Hydraulic oil FAQs

Hydraulic oil is vital for machinery and equipment subject to high pressure situations, heavy load bearing or extreme heat. Hydraulic oil transfers energy and power and the associated additives combat friction, corrosion and foaming. This makes hydraulic oil a vital component in the operating and maintenance of machinery and equipment.

Hydraulic oil typically has a high flash point to make it safe in extreme heat. The point at which hydraulic oil will combust varies depending on the specific oil grade, but industries that operate in high temperatures or near open flames, should ensure they choose an oil with the highest flash point.

As well as a large stock holding and extensive distribution network, Certas Lubricants is partnered with global manufacturers producing only the best hydraulic oils and fluids. This means we can distribute and deliver high quality hydraulic oil near you all year round and at a competitive price.

Hydraulic oil varies according to its specific purpose. Hydraulic oils designed for load bearing equipment will have a different set of additives to an oil designed for aircraft doors or die casting machines. Choosing the best hydraulic oil will depend on the specific needs of the user, and selecting an oil that cannot meet these needs can result in reduced performance or damaged equipment.

Virtually every industry in the world will use hydraulic oil in some capacity. The most common industries that benefit from hydraulic oil are those using heavy duty applications, such as agriculture, construction, aviation, marine and manufacturing.

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