Hydraulic Oil


Hydraulic oil

One of the most important oils in the automotive, heavy, aviation and aerospace industries is hydraulic oil. The main task of hydraulic oil is power transmission and lubrication in the relevant part. If you’ve ever felt the pressure of choosing the right hydraulic oil for your machinery, you’ll know all too well the minefield of information that’s out there in books or online. Instead of getting lost in the world of hydraulic fluid, hydraulic liquids or hydraulic lubricants, why not take a look at our easy to follow guide to hydraulic oil? It’s everything you need to know about hydraulic oils!

This type of oil makes the hydraulic parts move better and transfers power to other parts easily.

The role of hydraulic oil in the car is to act as a fluid to move the parts and speed up their movement.


types of hydraulic oil :


1- Type of petroleum oil: from crude oil refining & mineral bases , but is quality is good,price is low & good ,are in all  markets.


2-A type of synthetic oil that uses pressure and current factors to transfer power. Hydraulic oil has vital applications in passenger aircraft such as moving wing surfaces and landing gear, and in heavy industry pumps, jacks and cranes.


Oil performance depends on the correct viscosity of the oil, system type, operating temperature, acidity, R&O, absorption rate.

Moisture has the resistance of the oil layer.

Hydraulic oil standards are subject to the International Organization for Standardization (ISO) and some standards of important factories such as SIEMENS, ALESTOM, etc.


Hydraulic oil classification

The classifications of hydraulic oil are a subgroup of different fluids with varying performance levels. Below is a list of common hydraulic oil classifications and their respective descriptions:

  • HL – Refined mineral oils with anti-oxidation & anti-rust properties: Mineral hydraulic oil with good lifting ability & longer storage time in the system
  • HM – HL with improved anti-wear properties :Mineral hydraulic oil with good ability to prevent wear, improved by anti-wear additive and...
  • HR – HL oils with VI improvers:Mineral hydraulic oil with high capability and high improved viscosity index for car and elevator systems and...


For a detailed list, you can speak with our knowledgeable team by contact us alternatively, you can read our mail  explainer of esyekta website .  




What is hydraulic oil?

Hydraulic oil is a non-compressible fluid that is used to transfer power within hydraulic machinery and equipment. Otherwise known as hydraulic fluid, hydraulic oil can be synthetic- or mineral-based.
At  yekta co, as a hydraulic oil supplier, we deal with 99% of mineral-based hydraulic oils.
Although this useful fluid is commonly used in the transfer of power, hydraulic fluid can act as a sealant, coolant and lubricant within machinery and equipment.




The main difference between synthetic and mineral based hydraulic oil

The majority of oils which are produced are either mineral based or synthetic. Mineral based hydraulic oils are derived from crude oil fractions whereas synthetic hydraulic oils are made using chemically produced base fluids.



Synthetic oils can be formulated to impart superior physical properties in comparison to mineral oils, for example high temperature performance, biodegradability and oxidation stability.

What is hydraulic oil used for?

Hydraulic fluids are used in many applications across every industry. To give you an idea of the vast array of uses for hydraulic fluid and why industrial hydraulic oil is so important, here are 10 examples of equipment and machinery which use hydraulic oil:


  1. Forklift Trucks – The hydraulic system within forklift trucks and stackers is important to help power the incredibly strong forks which need to lift some super-heavy goods.
  2. Log Splitters – The ram mechanism on a hydraulic oil log splitter requires hydraulic fluid inside to give it that immense power which can split logs with ease. Log splitters are also known as wood splitters!
  3. Automotive Lifts – Car lifts (car jacks, automotive lifts, etc.) require hydraulic jack oil to aid their impressive power range! This type of machinery depends heavily on reliable hydraulic oil for safety as well as performance. Hydraulic fluid for a car lift tends to have a higher viscosity grade for high pressure.
  4. Wright Standers – A wright stander is a stand on mower which is usually well-suited to cemeteries and other restrictive grassy areas. The hydraulic part of these machines requires hydraulic oil for power.
  5. Snow Ploughs (Snow Plows) – Hydraulic oil for a snow plough and ploughing equipment is essential in the powerful operation of the hydraulic lift, tilt and angle movements of the snow plough blade. The cold weather conditions associated with the use of a plough means that the hydraulic fluid used in a snow plough will be blended with antifreeze additives.
  6. Skid Steers (Skid-steer Loader and Skidsteer) – Skid steer hydraulic oil is as versatile as the machine it works with. For the many tasks this machine can competently complete, hydraulic oil plays a big role at all times.
  7. Aircraft (aviation) – In the aviation sector, it is essential that aircraft hydraulic oil is reliable as it is used for aviation control systems, aircraft hangar doors, aircraft jacks and aircraft controls.
  8. Air Tools – Air tools and air compressors require high-pressure hydraulic oil which contains anti-wear additives for protection.
  9. Tractors – Tractor hydraulic oil is necessary for the operation of hydraulic brakes and hydraulic systems on agricultural vehicles and machinery. For your hydraulic oil tractor supply, you may want to use a reputable manufacturer to ensure your expensive machinery and vehicles are well looked after and protected.
  10. Cruise Ships and the Marine Industry – If you’ve been lucky enough to go on a cruise ship then you’ll have felt the comforts out at sea. Hydraulic oil is used aboard many marine vessels for the stabilisers. The stabilisers reduce the amount of roll, which can affect the ship’s balance and cause you to experience unfriendly sea-motion sickness. This is just one of the many other applications on marine vessels which require hydraulic oil.



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When it comes to hydraulic oils, viscosity is the measurement of its resistance to flow and it is an important property of hydraulic fluids. This means the fluid will resist compression at different rates depending on its viscosity and take longer to pass through an orifice as the viscosity increases.

Hydraulic fluid with high viscosity will be thicker and harder to compress and move as opposed to low viscosity hydraulic oil which will be thinner and pass through easier.




The viscosity of a hydraulic fluid is measured in Centistokes (cSt) and usually at temperatures of 40°C & 100°C. The value will always have the temperature next to it as without this the value will be meaningless. A fluid’s viscosity is measured in a petroleum laboratory using a viscometer !

Viscosity Index Improvers were first used to make multi-grade engine oils in the 1940s. These days, this common and well-tested technology is used to make high VI oils for other applications, including automotive transmission fluids and manual transmission gear oils. However, the VI improvers used in oils for the aforementioned applications are not typically shear stable when used in modern hydraulic systems.

But, recent advances in VI improver technology mean that mineral hydraulic oils with a shear-stable viscosity index in the 150 to 200 range are now commercially available.

While this may be good to know, what does it really mean to a hydraulic equipment owner? Well, within the allowable extremes of viscosity required to maintain adequate lubricating film thickness for hydraulic components, there’s a narrower viscosity range where power losses are minimized and, therefore, power transfer is maximized.

By maintaining the oil’s viscosity in this optimum range, machine cycle times are faster (productivity is increased) and power consumption (diesel or electricity) is reduced.

So, using a higher VI oil means the hydraulic system will remain in its power transmission “sweet spot” across a wider operating temperature range. You could think of this as similar to installing an automatic tensioner on the V-belt drive we talked about earlier in order to maintain optimum power transfer conditions.



Hydraulic oil viscosity is important for each different application.

Hydraulic oil is different than other lubes. Not only is it a lubricant, it’s also the means by which power is transferred throughout the hydraulic system. So, it’s a lube and a power transfer device. This dual role makes it unique.

To be an effective and reliable lubricant, hydraulic oil must possess properties similar to most other lubes. These include: foaming resistance and air release; thermal, oxidation and hydraulytic stability ; anti-wear performance; filterability ; demulsibility; rust and corrosion inhibition; and viscosity in respect of its influence on film thickness.

To be most efficient in its role as a power transfer device, hydraulic oil needs high bulk modulus (high resistance to reduction in volume under pressure) and high viscosity index (low rate of change in viscosity with temperature).

As an analogy, consider the tension on a V-belt. If it is out of adjustment, the belt will slip. The result is a higher percentage of input power wasted to heat. This means less power is available at the output to do useful work. In other words, the drive becomes less efficient.

A similar situation can occur with hydraulic oil. Change in its bulk modulus and/or viscosity can affect the efficiency with which power is transferred in the hydraulic system.

The wrong viscosity could cause damage to equipment or have poor results in function