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Good day,

I dont have very clear when to recommend which type of oil for hydraulic systems

In industrial applications it seems clear to go with an industrial dedicated product (for example Mobil DTE, Shell Tellus).

But in some on-highway / off-highway applications when i can't reach a OEM recommendations, i still haven´t figured out where and why i have to use whether an industrial product/ an ATF/ or a DEO SAE 10W (as long as viscosity is ok).

Could you give me some tips to consider ??
Many thanks in advance
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off highway tends to use either a motor oil type lube in hydraulic and transmsions or a UTF or universal tractor fluid which has a high EP load for use in hydraulics and final drives.

Rule of thumb if used in htdraulic ONLY then a Normal AW oil is OK.

If used in combination hydrualic and trans or final drive then a UTF is better due to higher EP requirment for final drives.
To add to bruce381's comment I would add that UTF tractor fluids also have friction modifiers for wet clutch and wet brake systems often found in tractors and fork lifts.

For many customers it's easier to stock UTF only and use it in everything than it is to stock both UTF and regular AW hydraulic oil. It also prevents someone from putting hydraulic oil in a system that needs the additional additives found in a UTF type oil.
Too complicated for simple advice, but lets try.
SAE 10W engine API >SF oil is roughly the right viscosity for hydraulics and by definition has good antiwear/antioxidant properties and is a bit expensive. (also CAT TO4 and Allison C4 10W and more expensive)
ATF Mercon, Dexron, TASA, Ford M2C33G all suitable for hydraulics again more expensive.
Tractor transmission oils UTTOs and UTF(a bit viscous) all OK in hydraulics(expensive)
Inexpensive solution Mobil DTE Anti wear, Shell Tellus or eqiv.(where appropriate)with wider viscosity choice for ambient conditions.
For fine filtration systems always chose bespoke hydralic oils.
DEO? Are we talking about Caterpillar? If so, which info do you need?

It really depends what type of system you are going to use the oil in. If it's just a hydraulic system, the fluid only needs to be:
- clean enough for economic filter life
- non-compressable, no foaming
- right viscosity
In this case, the hydraulic oil only serves as a medium. Therefor you see so many differentiations, one OEM uses engine oil, the other a straight hydraulic oil, another ATF, etc.

@Michael: Can you give an example of a typical UTTO/STOU characteristic which may be required for a regular hydraulic system?
Last edited by em
You need to be very careful with which hydraulic oils are used particularly in off highway mobile fleet equipment. For example, Caterpillar requires the hydraulic oil (generally TO4 style or engine oils) to have a minimum of 900ppm of zinc. Hitachi on the other hand recommend their own product which is a HV style oil especially when under warranty. It may pay to get a lubricant survey done either in house or via your oil supplier which lists all your fleet, compartments and oil types used meeting OEM requirements. This needs to be available for all the site persons. Mobile fleet equipment are generally not very complicated in terms of their requirements - typically 5 or 6 oil types are all that is needed.

in line with the previous information about CAT i found the datasheet and they recommends that... “Industrial hydraulic oils may shorten hydraulic pump and component life because they
typically omit or contain reduced levels of the additive agents listed in this publication.
Industrial hydraulic oils are usually formulated to separate water from the oil, a desired characteristic for stationary hydraulic systems. However, in earthmoving equipment this
separated water will cause pump and component damage if it is suddenly drawn through the
system from the tank as the machine moves.”

From Komatsu a similar observation... “There has been a lot of discussion on this subject, but as of this date, the only product recommended by Komatsu for hydraulic system use is SAE10W engine oil that meets API specification CD (or later specification in this series) or MIL-L-2104. At this time, the use of AW series hydraulic oils, such as AW46 are not recommended.”

The use of SAE 10w appears to be the recommended option for hydraulic systms in off-highway equipment (p.e. cat / komatsu). It seems that industrial hydraulic oils dont have the appropiate level of additives.

What problems could i encounter if a sae 10W is used in an industrial hydraulic system, as long as viscosity is the recommended?
When an ATF is considered an option as hydraulic fluid... ?

Most industrial or fixed plant hydraulic systems tend to use "hydraulic oils" such as HLP or HV types etc. The problem with using an SAE 10W is the demulsibility characteristics (water separating qualities). Industrial hydraulic oils are designed to separate from water easily. Engine oils on the other had contains detergents which has a tendency to hold or emulsiy the water.
The other issue is air release qualities (always done on all industrial oils - check technical data sheets of oil supplier)- an ISO VG68 oil for instance will have an air release of 6 to 8 mins. It's important so that the hydraulic operation is not spongy and you want rapid response. This is not a typical test or characteristic of engine oils.
Multigrade engine oils (eg 10w/30)also contain a viscosity index improver polymer which are sheared down (ie chopped up)when used in hydraulic systems both mobile and fixed plant application - shown as the reduction in viscosity. The rate of shearing is dependent on the type of pump ie piston or vane or gear.
Filterability is also important - industrial hydraulic oils are checked for filterability - as there are many fixed plant applications with fine filters. This is not a test done for engine oils in general.
A few OEMs recommend an ATF style fluid - most ATF fluids are equivalent to an ISO VG 32 or so hyraulic oil. Not exactly sure why but it can be down to their experience with ATF fluids only and not much experience with hydraulic oils. Many ATF fluids are made on a high quality base oil (eg group III or higher)which imparts oxidation stability to the oil.
However, most hydraulic oils are made on quality base oils with very good antioxidants.
I hope this helps.

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