Hydraulic fluid replacement for 10w 30

Messages
21
Location
Connecticut
I searched around a little but didn't really find a whole lot on this here.

I have a skid steer that calls for 10w-30 engine oil for the hydraulic system. I am going to change all 15 gallons and I think I would like to go to a hydraulic fluid instead of the 10w 30. I understand that 10-30 will "do the job" but I can't see why a less expensive hydraulic fluid won't also do the job and maybe provide some benefit with regard to moisture.

For example: Mobil tractor hydraulic fluid says "Outstanding replacement for engine oils recommended for hydraulic and transmission systems" However, the Mobil THF says replacement for GL-4 or 80W. Which may be too heavy weight ?

Can someone make a recommendation for a Hydraulic fluid to replace the 10w 30 ? Brand or not is fine (I can select my own brand).

Would I be looking for an ISO 100? ISO 32? in between ?

Thank you
 
Messages
998
Location
UK
SAE 80W gear oil (using SAE J306) is equivalent to a 20 or light 30 grade engine oil at 100°C, so in the right region. However it depends on how hot the hydraulic system runs - they tend to specify viscosity at 40°C (which is what the ISO VG are) so direct comparison from engine/gear oil to hydraulic oils is not easy as you need to know the KV40 of the engine oil, which will depend on its VI - none of this is part of the engine oil viscosity classification (SAE J300).

It looks like the Mobil THF is a good replacement from a viscosity perspective - I can't comment on its suitability in your specific system, nor if the requirement for engine oil is not just driven by viscosity but also by some other factor that engine oil will cover (seals, detergency, antiwear etc).
 

MolaKule

Staff member
Messages
21,686
Location
Iowegia - USA
See this read across chart for engine oil "Grades" and ISO Hydraulic fluids:


A suggested Hydraulic fluid would be this fluid in ISO 68 or 100 viscosity, depending on start-up temps:

 
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Fortecarbon

Thread starter
Messages
21
Location
Connecticut
I thought I had read that 80W was close to a 10w 30, but then I figured I may have had that wrong. So SAE rates "engine" oil and "gear" oil differently (brilliant).

I am in the North East (Connecticut) and the machine is just for my around the farm fun work, so I can probably get away with a lighter weight than a machine that is moving asphalt around all day on a construction job.

A skid steer hydraulic system is pretty straight forward, there really aren't any bearings, gears, etc to deal with except the pump and motors. I don't know why I didn't think to to this before... but I figure the tandem pump is the most complex thing in the system, so I looked up info on it (Sauer model 46). See attached PDF for fluid specs...

"Ratings and performance data are based on operating with premium hydraulic fluids containing oxidation, rust, and foam inhibitors. These include premium turbine oils, API CD engine oils per SAE J183, M2C33F or G automatic transmission fluids (ATF), Dexron II (ATF) meeting Allison C-3 or Caterpillar T0-2 requirements, and certain specialty agricultural tractor fluids. For more information on hydraulic fluid selection, see Sauer-Danfoss publications: 520L0463"

I will read their publication.
 

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MolaKule

Staff member
Messages
21,686
Location
Iowegia - USA
...Can someone make a recommendation for a Hydraulic fluid to replace the 10w 30 ? Brand or not is fine (I can select my own brand).

Would I be looking for an ISO 100? ISO 32? in between ?

Thank you
A number of suggestions have been made in response to your original question.

Is there another question?
 

Fortecarbon

Thread starter
Messages
21
Location
Connecticut
Sure... I can muster another question.. :) Viscosity Index.... I understand this is probably wildly oversimplifying but VI is the measure of a fluid viscosity stability over a temperature range. So if I am comparing different fluids and other things being equal, a higher VI would be desirable ?
 
Messages
385
Location
Greenville SC
So if I am comparing different fluids and other things being equal, a higher VI would be desirable ?
It's very unlikely other things will be equal, but yes, a high VI would be better. In MY OPINION, the best hydraulic oils are the Mobil DTE20 series. They have a low VI meaning that temperature control is important. IN GENERAL, high VI fluids are not optimum for hydraulic applications; when they shear, you lose some of that VI.

There are very knowledgeable folks here who disagree with me, but if I need a high VI fluid, say for a system that needs to run at -40 degrees and at +160 degrees, I recommend a good ATF, but an older one. The new formulations have issues with older seal materials. In particular, Dexron 6 and 2010 era seals had issues.

I used to suggest Mobil synthetic Dexron 3 ATF, but that product went away when GM updated their specs, and won't allow old specs to be advertised.

You've been sent links to viscosity charts. Choose a fluid with an operating temperature viscosity in the 16-50 cSt range, and that is thin enough to startup with your equipment in your lowest temperatures. You should, if at all possible, allow the system to run substantially unloaded until the fluid gets to at least 70F or so. Unless your system gets over my 160F magic number, MOST fluids that are in the 16-50 at operating range will be safe (but not optimum) at 160F. The AW46 mentioned will be pretty good unless you need to startup and run when cold.
 

Fortecarbon

Thread starter
Messages
21
Location
Connecticut
Thanks for all your feedback and suggestions.

I think I am going to go with the Mobil Tractor Hyd. fluid. for a couple reasons. 1) Its priced well and more importantly easy for me to get - in stock locally or free shipping online. 2) Meets Allison C-4 and Cat T-02 specs specifically mentioned in the pump data sheet. 3) Falls within the viscosity spec of the pump 4) Meets Kubota UDT specs - and I have already used it in one small Kubota I have (I think I used Chevron THF in my larger kubota). So its a one and done for my hydraulic fluid needs.

Thanks for all the great info.
Clint
 
Messages
385
Location
Greenville SC
Assuming you are talking about Mobil Delvac™ Tractor Hydraulic Fluid, it looks like a good choice. It has viscosity similar to a AW32 at 20F, to a AW46 at 120F, and a to an AW68 at 220F. Good VI of 145.

To the extent practical, operate the hydraulics unloaded (low pressure) until it warms up to a moderate temperature; with that VI, you could go a little lower than the 75F I mentioned, but 90F-100F would be better.
 
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