ADDINOL hydraulic oils for any application

ADDINOL hydraulic fluids are ideally suited for use in stationary and mobile facilities. They are also suitable for special operating conditions, e.g. in fire-prone facilities, ecologically sensitive areas or in the food industry. Their performance far exceeds the minimum requirements of DIN 51524. Thanks to the ideal combination of high-quality base oils and carefully selected additives, they master the challenges of modern facilities, such as compact designs with small oil volumes, high operating pressures, improved surface treatment and special temperature conditions. They offer reliable protection against wear and corrosion in all applications. In addition, many of the ADDINOL hydraulic oils are designed for energy efficiency.

Your benefits at a glance:

  • outstanding air release properties with low foaming tendency
  • very good demulsibility and good water separation ability
  • excellent wear protection and very good aging behavior
  • high thermal-oxidative stability
  • improved corrosion protection
  • high purity
  • Excellent, personal service thanks to our Application Technology

Hydraulic oils by type/viscosity

If you already know which hydraulic oil with which characteristics meets your needs or the manufacturer's specifications, you can delve deeper into the subject matter with our pre-selection of the most important classes of hydraulic oils.

Requirements on hydraulic oils in use

Whether agricultural equipment, tractors and wheel loaders, industrial applications such as presses or injection moulding machines, but also heavy truck tippers or municipal vehicles in road traffic, we encounter hydraulic systems everywhere in everyday life. The requirements for the use of hydraulic fluids are versatile and increase with the further development of the technologies applied. More compact designs, smaller oil volumes and special design features (e.g. smaller lubricating gaps) mean higher temperatures, pressures and loads for the lubricant used. In addition, the systems are often in operation around the clock and operators place high expectations on their efficiency. The quality of the lubricant used has an impact on the service life and productivity of the systems. Here, lubricants are demanded which meet the requirements perfectly and ensure the reliable operation of the systems at all times and with maximum efficiency.

Hydraulic excavator in a coal mine
Without a well-oiled hydraulics, no excavator works

Differences in hydraulic oils

The specifications defined in DIN 51524 represent the minimum requirements on hydraulic fluids. For most hydraulic systems, manufacturers specify fluids according to DIN 51524 Part 2 ”HLP“ or Part 3 ”HVLP“. The corresponding minimum requirements refer to demulsifying capacity, purity level, air release properties and filterability. In addition, compliance with the desired viscosity class and viscosity-temperature behaviour are important. Hydraulic oils are therefore composed of high-quality base oils and, depending on the application, varying additives.

Hydraulic fluid Description Properties
HL Against oxidation and corrosion Improved corrosion protection
HLP Against oxidation, corrosion + anti-wear additives Ageing-stable, corrosion protection, operating temperature approx. -20 °C to + 80 °C
HVLP Standardized to DIN 51524-3, VI is at least 140 Better viscosity / temperature behaviour, application advantages at "limit" temperatures, fluctuating operating temperatures, operating temperature about -35 °C to + 120 °C
HLPD Detergent and dispersant additives Applicable for sensitive controls, prevents sludge formation, operating temperature approx. -20 °C to + 80 °C
HVLP D Detergent and dispersant additives, VI is at least 140 Prevents sludge formation, high viscosity index
Arctic Fluid Good flowability at low temperatures Special hydraulic oils for cold chambers, and very low outside temperatures
HEES Not environmentally hazardous, high VI Biodegradable ester-based hydraulic oils (saturated / unsaturated), resistant to ageing, temperature resistant
HV Eco Fluid Standardized to DIN 51524-3, VI is at least 140 Mineral oil based, very good VT behaviour, very well suited for external hydraulics, significant energy savings, less fuel, less CO2
Hydraulic system of a bulldozer
In heavy machinery such as bulldozers, hydraulic oils must absorb large loads

Viscosity of hydraulic oils

In addition to reliable control of impurities of all kinds, the flow behaviour of hydraulic fluids during operation and above all at limit temperatures plays a decisive role. These properties are described by the viscosity index and influence the reliable lubrication of all components. The VI is calculated from the kinematic viscosity at 40 °C and 100 °C. A low VI value means a poorer oil penetration at low temperature and a high viscosity drop in the heat.

At cold start or outdoor use, the quick supply of all lubrication points must be ensured in order to guarantee the functioning of the system. If the flowability of the lubricant used is insufficient, fatigue and wear occur. This results in slow reaction times and increased energy consumption. Even at high temperatures, a stable lubricating film must be ensured; otherwise, wear and cavitation may occur. The high quality of the base oils used with a naturally high VI and additives ensures best response behaviour and maximum efficiency at all temperatures when using ADDINOL hydraulic oils.

The viscosity of hydraulic oils is not a quality feature. It is specified by the manufacturer anyway, depending on the application. For instance, there is the hydraulic oil HLP 46: HLP stands for the type of hydraulic oil, the 46 describes the kinematic viscosity (mm2/s) at 40 degrees Celsius. The viscosity is defined by the internal friction of a liquid. This is always temperature dependent. At low temperatures, the viscosity increases. At higher temperatures, the viscosity decreases.

Oil flows into a bowl
The viscosity of an oil determines how thick or thin it is

Colour of hydraulic oil

The colour of the hydraulic oil is not an indicator of the quality of the product. Depending on the manufacturer, the fluids may be coloured green, red or blue. Many things are possible. However, this does not indicate whether the hydraulic oil is better or worse than another. Also, the colour of the oil does not determine its ageing or usefulness. Although the fluids can change their colour through ageing, they still do not allow any conclusions as to whether they still fulfill their requirements. The colour may also change due to the entry of water or dirt particles or be influenced by the diesel effect. If the colour of your hydraulic oil changes a lot, it's best to send it to the lab for analysis. There it can be determined with certainty, whether the oil has become unusable or can be used without hesitation. Examined components such as viscosity, degree of contamination, additive degradation or water content provide information about the further procedure.

Oils with different colors in sample cups
The color of an oil does not determine its properties

Filterability of hydraulic oils

Manufacturers define the maximum permissible degree of contaminants for their systems and components: the so-called purity level. The purity level is an indicator of how carefully the oil has been produced and filled. According to DIN 51524-2 (HLP) and DIN 51524-3 (HVLP) the following purity level is required: 21/19/16. If the oil used does not meet these requirements, there is a risk of negative effects on the function and performance, but also on the service life of the components. Possible consequences range from wear and deposits to complete functional failure. Impurities carried in represent an enormous danger for the function of seals and control valves. By improving the oil cleanliness or reducing the particle content, a significant extension of the operating time can be achieved.

Diameter of the smallest particles in the hydraulic oil
Small particles in the hydraulic oil can cause considerable damage to the system

Air separation capacity for hydraulic oils

Lubricating oils contain air, which has no negative effects on lubricity and system components in dissolved form. If there are pressure and/or temperature variations, however, dissolved air can be released resulting in air bubbles. Besides, it is difficult to avoid the introduction of air during operation. Air bubbles impair the lubrication and cooling performance of a lubricant. They lead to compressibility, i.e. the optimum control of the components is no longer guaranteed. The first sign of this is often increased noise generation in the unit. If free air is present in the system, pumps must deliver a higher output. Energy losses and a reduced service life of the components are the result. Cavitation and the so-called diesel effect also occur. For the lubricant itself, the introduction of air leads to accelerated ageing.

Foaming in hydraulic fluids

The introduction of air, impurities, oxidation, but also special design parametres can lead to foam formation during operation. Foam impairs the lubricity of a hydraulic oil and prevents optimum power transmission. In addition, foam leads to abrasive wear and entails risks for the environment, as it promotes oil discharge. Thanks to the careful formulation, ADDINOL hydraulic fluids achieve the best values for foaming behaviour and thus ensure optimum lubrication of the systems. Experience from our analysis service shows that supposedly inexpensive hydraulic oils cannot do without the addition of defoamers based on silicone oil. These are surface-active, i.e. they settle on the lubricating film and are filtered out. This means that reliable protection against foam formation is no longer guaranteed. The only effective way to solve the problem is to find the cause and eliminate the cause. The addition of defoamers is not a permanent solution.

Foaming behavior oil, air intake in oil
Air in the oil, left (oil without foam inhibitors) forms more foam than on the right (oil with foam inhibitors)

In the experimental setup above, air was added to two oils over a period of five minutes. The oil without defoamers (foam inhibitors) forms much more foam than the oil with defoamers. However, the defoamers do not completely prevent the foaming. It is obvious, that there schould be added as little air as possible to the oil.

Demulsibility of hydraulic oils

After contamination by solids, contamination by water is the second most common cause of failure for hydraulic systems. According to DIN 51524-2 and 51524-3, the water content in a fresh oil must not exceed 0.05 %. ADDINOL hydraulic fluids have a very low water content of approx. 0.01 % and therefore offer the best preconditions to minimize the risk of corrosion. Due to humidity in combination with temperature variation, but also due to incorrect storage of the fresh oil, the water content in the system can be significantly higher. The direct introduction of water is also possible and difficult to avoid. Cooling water leaks, cleaning and maintenance measures and the production process itself can lead to water ingress. If the free water is separated or forms an emulsion with the oil, the performance of the lubricant is considerably impaired. In addition, accelerated oil ageing, corrosion and damage due to cavitation and wear occur. Demulsifying behaviour therefore plays a major role in many hydraulic systems. For oils with good water separation properties, free water can be optimally separated from the oil and simply drained off. The ADDINOL hydraulic oils of the class HLP and HVLP have the best demulsifying behaviour and thus provide reliable protection against corrosion, cavitation and wear. Optimum lubricity is guaranteed even under difficult conditions.

Demulsibility of fresh and used oil
High-quality hydraulic oil (left) separates faster from water than used oil (right)

Mix hydraulic oils

Not all hydraulic oils are miscible. You should avoid the mixing of oils with the following properties or compositions:

  • Zinc-free and zinc-containing additive systems
  • Detergent and non-detergent oils
  • Base oils with glycols
  • Different base oils (HFD, HEES, etc.)

To avoid mixing mistakes, it is best to maintain a lubrication schedule and always make a note of the oils you are using. When refilling, pay attention to the usability of the current product. Mixing two hydraulic oils that are incompatible by accident may significantly affect the functionality of the hydraulics. Damage to the material until total failure is inevitable as the oil does not lubricate properly anymore. In this case, drain the oil, clean the hydraulic system and fill with new oil.

Change hydraulic oil and dispose it properly

The change of the hydraulic oil is specified by the manufacturer depending on the machine. It is best to follow the instructions and the defined replacement intervals. In addition, the oil change should always be made when the oil properties change significantly. These include signs such as changes in viscosity, contamination and depletion of the additives. In case of uncertainty, you can always send the oil to the laboratory for analysis. ADDINOL offers you the possibility to carry out oil analyzes. In the course of this, the oil is evaluated professionally and thus it can be determined whether it can continue to be used or not.

If the hydraulic oil no longer fulfills the desired requirements, it must be drained and disposed of. To do this, put the used oil in a shatter-proof container and place it in the waste oil collection point of the recycling depots in your local community. The seller of the oil is also obliged to accept the used oil. In that case you have to return the waste oil or send it by post. Even if the disposal of the old hydraulic oil is inconvenient, take the task seriously. Hydraulic oil, which enters the groundwater in an uncontrolled manner, can cause enormous environmental damage. In addition, high fines are associated with it.


Sara Schmorl

Dr. Sara Schmorl

Product Manager Industry Lubricants

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