Hydraulic System specs using Motor Oil or ATF

[Bill80401]

The hydraulic system on my backhoe/loader specs using API 10W-40 SF-CC rated motor oil, or Automatic Transmission Fluid (ATF) .... this is not for the Hydrostatic drive system (that uses ATF), but for the actual (separate) hydraulic system that powers the backhoe and loader cylinders .........

The guys where I had a hydraulic cylinder rebuilt laughed when I told them this and said I should only use Hydraulic Fluid, that motor oil doesn't have the compression that hydraulic fluid has ...

I've done a complete overhaul to the hydraulic system .. I've removed every cylinder and opened them up, inspected them and cleaned them out. I have taken every line apart and blew them out with an air compressor ..

.... The system is completely empty.


I now need to decide what I am going to refill it with .............. do I use motor oil, transmission fluid, or 'tractor' hydraulic fluid ???


If I go with motor oil, do I need to find a non-detergent oil, or can I use 'off the shelf' motor oil ?? (like for example, O'Reilly Auto Parts sells its cheap brand of motor oil) .. I guess I have the same question for using ATF ... again, just an off the shelf ATF ??

If I go with Hydraulic Fluid, I see that some are an ISO while others are an AW rating (for example: I find AW32 and ISO32 hydraulic fluid) .. what is the difference ?? ....... Which is what, and which is right for me ??? .....

I've found "General Purpose Tractor Hydraulic Fluid" with no ISO or AW rating .......... so what is that stuff ?? ...

 

[Whatswrong]

Just my 2 cents and I may be wrong ,you are running a self contained system ,go to Walmart and buy the cheapest hyd oil you can ,it will have a low enough viscosity to not give you grief in cold weather .The engine oil may be to thick.The company I work for used 15-40 engine oil at one time but it was a summer use product only now they use hydraulic oil .

 

[MHarryE]

The people who rebuilt your cylinder are wrong. Engine oil in general is a very good hydraulic oil for mobile equipment except for one problem. Unless you find a very poor quality oil, the engine oil will be very expensive. It will have additives to handle combustion by products that get past the rings. If you search the web for Caterpillar hydraulic system fluid recommendations, you will find DEO (diesel engine oil) listed as suitable for nearly every hydraulic application and the only oil for some applications. In general, 15W-40 DEO is the preferred oil wherever the ambient temperature exceeds 40 degree C (104F). In the Persian Gulf region I have seen them drain factory fill oil and refill with 15W-40 to ensure hydraulic pump and motor life. In piston pump and motor applications, however, close clearances and high pressures cause multi-viscosity oils to shear down so after a few hundred hours a 10-40 oil may be closer to a 10-30. This is really true for non-synthetics. Unless I ad some later information from the mare like a service bulletin changing the oil spec, I would go with the book recommendation.

 

[JoeBuyer]

I use hydraulic oil in hydraulics, engine oil in engines. That's why they make different kinds, different additives. I would agree that you don't need to break the bank and get the highest priced kind you can find and in that case there is not that much of a difference. Old tractor specs are outdated from a time when we did not have the selection we do now. But today's fluids can benefit your older machines too.

 

[CJONE]

Bill go with either a AW32/AW46 hydraulic oil or tractor 303 oil. Basically like was stated whatever you can find the cheapest. Engine oil not having the "compression" hydraulic oil has. BS they are talking out their butt. MHarryE is giving you good info.

 

[J_J]

A lot of equipment manufacturers recommend motor oil in the hyd system.

My Power-Trac hyd fluid is 10W-40 and the Power-Trac line of machines have been using it for over 20 years.

If your machine manufacturer recommends motor oil, then use it. The hyd fluid in my Case 1845 skidsteer is 10W30, with alternates of HYGuard, or ATF.

If you are going to change fluid types, be sure to remove all the old fluid, or as much as you can.

 

[Bill80401]

Here is a response someone sent me on the side ..

I'm pasting it in here because it has some very useful advice and information that I think should be available to anyone else seeking answers on this topic ....




<< BEGIN QUOTE >>

That motor oil compression comment is worth a laugh. You should go back there and play dumb and ask them for further explanation.

I don't deal with any automatic transmissions, so my knowledge on those fluids is a little dated. Like everything else, we are getting into all types of custom fluids and specifications today. I would be initially inclined to use an ATF since that's what your hydro uses. It's additive package is probably a closer match for hydraulics than motor oil. However, what type? I'd say to use a type A Dextron, but there are several upgrade levels of Dextron. The various Dextrons are supposed to be backward compatible, so they might be a good choice. Chrysler has some very specialized fluids, their +3 and +4 types that even they can's keep straight, so I would avoid them. That leaves Ford's old type F that has a special friction modifier for clutch plates, so skip them.

Your motor oil API SF/CC classification is also dated. The chemistry in recent motor oils have changed a lot due to emissions. Some additive items like phosphorus and zinc have been reduced or eliminated. Other items like anti sludge cleaners have been added. Because of this and common motor oil doesn't have a lot of anti foaming properties, I'd consider motor oil as my last choice. Certainly synthetic would be better than dino.

That leaves hydraulic fluids, and that's what I'd go for as first choice. The additive package is proper for the use. Pick any type and it should be equal or better than what was originally specified. You don't have to worry whether or not the newer additives in motor oil are compatible with seal material that was used several years ago.

1) Hydraulic fluid

2) Type A ATF (definitely not type F)

3) Synthetic motor oil (Shell Rotella T6 5W-40 is a good choice)



<< END QUOTE >>

 

[Bill80401]

I've got to say thank you to all of you for some great information and advice ....

I think I'm going to go with hydraulic fluid in the system. I found AW32 hydraulic fluid available in 5 gallon pails at my local auto parts store (O'Reilly Auto Parts) for $45, and they have it on the shelf in gallon sizes too if I need to top off ..

I guess I just can't wrap myself around using motor oil in the hydraulic system ...............