Hydraulic System

Totally confused;

My local Hustler dealer says I should not use an oil with Zinc additive but recommends a synthetic in the hydraulic transmission.

(Both of the oils, mentioned above, have Zinc)

The various oil manufactures technical advisors say that this older Hydro Gear system and I should use a mineral oil eg 20w/50

Hustler Service Manual is apalingly non specific;

"The mower ships from the factory with SAE 20W50 oil in the
system. Use SAE 20W50 oil, 15W50 synthetic oil, or 20W50
synthetic oil when changing the system oil and filter. Hustler®
Full Synthetic 20W50 Hydrostatic Transmission Oil is
recommended.
Fluid level should be 1" (25.4 mm) from top of reservoir.
Figure 4-4
NOTE: The reservoir will require approximately 3.0 U.S. gallons
(11.35 liter) of SAE 20W50 oil, 15W50 synthetic oil, or
20W50 synthetic oil when replacing the oil after an oil and filter
change"

Hydro Gear are even worse.


What is your advice??

:devilish:
 
Hello Skippy,

Oh No! Not the "evil Zinc" .... Just another scare from an uninformed individual who has been misled by rumors that Zinc is some kind of "destructive" additive in oil. The dealer of all places should know better, but people are quick to believe bogus rumors instead of reading the actual legitimate published data on the subject.

Zinc (ZDDP) is what helps oil endure stress and heat.

It is mainly critical for the amount of Zinc in gas engines with catalytic convertors or diesel engines with DPF systems. Zinc actually contaminates these devices.

Inside a hydraulic drive unit, it is actually beneficial to have it.

Go online and check out the "Bob the Oil Guy" website.
 
Hi Auto Doc,

Thanks for the above however you haven't actually commented on straight 20W/50 motor oil V a synthetic 15W/50 with Zinc.

I tried to register on the "Bob the Oil Guy" website - ran into problems, so at the moment unable to discuss the options with Bobs members.

Also having difficulty sourcing the OM hydraulic oil filter PN 783936 (EXCEL Industries filter). Do you have any suggestions for an alternative.

:devilish:
 
Auto Doc's said:
Check this out:

ZDDP in engine oil - Search Videos

Watch videos instantly on Bing—enjoy direct playback, discover related clips, and dive into trending content all in one place.
www.bing.com www.bing.com
Click to expand...
Hi Auto Doc,
Dont know if its the Video or something else but it was almost unwatchable due to advertising breaks.
That aside - Zinc would certainly seem to have significant wear reduction characteristics.
Remembering that this is an old machine with unknown oil in the hydraulic system (some contamination of new oil) - would you go for the "Full Synthetic" 15W-60 with "Full Zinc" or the mineral 20W-50???

:devilish:
 
Skippydiesel said:
Hi Auto Doc,
Dont know if its the Video or something else but it was almost unwatchable due to advertising breaks.
That aside - Zinc would certainly seem to have significant wear reduction characteristics.
Remembering that this is an old machine with unknown oil in the hydraulic system (some contamination of new oil) - would you go for the "Full Synthetic" 15W-60 with "Full Zinc" or the mineral 20W-50???

:devilish:
Click to expand...
Hi Skippy,

Given the two choices, I would go with the full synthetic and do not use any additional additives because the oil has a sufficient amount already.

For most units I personally use 20W-50 regular conventional oil. It works well for me down here in South Texas
 
Last edited:
Skip the Super Z here actually uses SAE 10w40. I also primary use Mobil One SAE 15W50 Full Synthetic in just about everything except the Tuff Torq which get SAW 5w50 synthetic. But of I get some fairly hot Summer days.
 
Thanks Auto Doc/ StarTech,

My origination choice (before confusion set in) was a Full Synthetic + Zinc 15W/50 however the Full Synthetic + Zinc 15W/60 (same oil company) is "On Special Sale" for a lot cheaper.
Other than cost saving, I also thought that the higher viscosity may be beneficial in an old hydraulic system and in Australia's notoriously hot summers. A Win, Win, Win - if you like.

Is my rational wanting or on the ball??

:devilish:
 
I have ordered the new oil filter so should be replacing the oil early next week -

How much effort should I put into removing the old oil ie is it necessary/desirable to try & drain the pumps & motors??
OR
Is the amount of old oil (unknown type) remaining such a small percentage, that it will have little if any effect on the new oils ability to perform??

:devilish:
 
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