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I have an older Troybilt ('94) lawn tractor with an Eaton 851 hydrostat. The oil cap says "20W oil" on it. Do they mean regular 20w engine oil? If so where can you buy it? Is there something else I can use that is 100% safe for my hydrostat? I have had it since new and have had zero problems with the unit and don't want to put something in that is going to damage it in the long run.

Likely they do. I'd look on the internet and see if I could find a local retailer. Advance Auto or Autozone might have it.

Okay, it won't be easy. I just searched Advance Auto and Autozone and they only had 30 wgt and 40 wgt. All the "20's" were x-20 or 20-x multi-viscosity.

I think they are referring to 20w hydraulic oil and not engine oil. 20w-20 oil is what I bet they are referring to.

OK, I may have found the answer to my own question via a Google search. "Fluid Recommendations
Premium hydraulic oil having a viscosity
equivalent to SAE 20w-20, SAE 30 or SAE
40". So I guess I can use a SAE 30 hydraulic oil.

I have an early 90's model Snapper with an Eaton in it. It recommends the same fluids as yours. I use 30w in mine.

Thanks for the replies. I still haven't added any fluid because I don't want to mix fluids. I would like to change the fluid but I'm not sure of how to drain it. Service schedule has no recomendation for changing fluid, only the filter. Parts manual doesn't show a drain plug and I haven't found one. I did find a small plug at the bottom of the unit but I am afraid it may hold something together inside the unit so if I take it out I could cause serious problems.

Eaton has used 20 wt (Motor Oil) for a Long time... they recently, about 10 years ago approved multi-vis Synthetic Motor Oil... I have used both 20 and 30 wt in Eaton's And have switched them over to Mobil1 15W-50 ...
Don't use hydraulic oil in Eaton pumps...
Using motor oil, they are nearly indestructible...
Synthetic Motor oil is completely compatible with the oil in there... But I would drain out all that I could, (older oil will shear down)...

You could stay with a 20 wt Motor oil if you are using it in an area in colder temps... if it is primarily used in Hot summer use 30 wt... But you will be much better with the 15w-50 Synthetic Motor Oil...
:smile:KennyV

What plug are you referring to that may hold something together inside? I can't place it... Could you post a picture of it...:smile:

Here are a couple pics of the plug. It takes a 3/16" allen wrench. I tried to loosen it to see if it had any resistance on it coming out but I couldn't even get it to break loose. It may need to be heated a little so that I don't strip it out. I know that some vehicle transmissions have plugs that look like they would be a fill plug, but if you remove them, things come apart inside the trans and you are left doing a teardown. Don't want this to happen!

Toptech said:

Here are a couple pics of the plug. It takes a 3/16" allen wrench. I tried to loosen it to see if it had any resistance on it coming out but I couldn't even get it to break loose. It may need to be heated a little so that I don't strip it out. I know that some vehicle transmissions have plugs that look like they would be a fill plug, but if you remove them, things come apart inside the trans and you are left doing a teardown. Don't want this to happen!

Click to expand...

^ No one knows what that plug/screw is?