New Z121S

mickeyd

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2014 L3200 DT w/LA524 FEL, 2019 Kubota Z121S w/ 48" Pro Dec, TG1860G w/RCK54TG
Mar 21, 2014
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Guin, AL
I just got the wife a new Z121S. :D

While going over the manual, I was amazed to find that the Transaxle uses "Engine oil: API service Classification SL SAE20W-50" instead of hydraulic oil.

Any other Z121 users out there have a recommendation on which brand oil to use?
 

lugbolt

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ZG127S-54
Oct 15, 2015
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I am NOT starting an oil war. They come pre-filled with a synthetic 20w50 and that's all I'm saying about it. Bad Boy among many others use the same transmissions. I have personally tested/used many different types/brands of 20w50 and there is zero difference between any of them. The Z121 HST's? That's the one part of a Z121 that I have not gone into, period. To me, they're bulletproof. Leave them alone and use the mower as it's designed to be used and don't overthink it and IMO you will never have an HST problem.
 

Daren Todd

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Massey Ferguson 1825E, Kubota Z121S, Box blade, Rotary Cutter
May 18, 2014
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Not trying to start an oil war :D Just a comment about pricing. When I went to service my Z121S, i stopped by the local kubota dealer for filters. Also needed parts and filter for my in-laws four wheeler. They happened to be the local Yamaha dealer as well.

I almost bought the oil I needed for both the mower and four wheeler from them. Till I saw the prices. Then I about fall off the stool at the parts counter :eek::):p I said never mind, I'll shoot across to the auto parts store for the oil. Kubota was pretty proud of there 20w50.

Valvoline, mobile 1, chevron, Quaker state are all good oils. All have to meet the same standards for today's equipment. Even the store brand oils are good.It just what you are comfortable paying for price and personal preferences.
 

mickeyd

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2014 L3200 DT w/LA524 FEL, 2019 Kubota Z121S w/ 48" Pro Dec, TG1860G w/RCK54TG
Mar 21, 2014
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Guin, AL
Sorry, I didn't mean to start "an oil WAR." :eek: :confused:

Thanks for the replies. :)

What struck me the most, was that it was neither hydraulic or gear oil. :confused:
 

North Idaho Wolfman

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Older Bobcats use motor oil in all of there Hydraulic systems too, it struck me as odd also, but it's to keep the drive motors clean as the Motor oil has a detergent in it. ;)

I will second or third, I might have lost count, Good quality synthetic 20W50 motor oil.
 

Russell King

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Sorry, I didn't mean to start "an oil WAR." :eek: :confused:

Any time someone asks about oils there tends to be slightly differing opinions vociferously expressed. Thus the fear of reprisals is great for any statements on any oil subject.



Sent from my iPad using Tapatalk
 

mickeyd

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2014 L3200 DT w/LA524 FEL, 2019 Kubota Z121S w/ 48" Pro Dec, TG1860G w/RCK54TG
Mar 21, 2014
1,192
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Guin, AL
I am having trouble finding a Full Synthetic 20w50 oil except for "Lucas Racing Oil" at $171.99 for 5 gal.
 

eserv

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BX24, A1000 Kubota Generator
May 27, 2009
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Older Bobcats use motor oil in all of there Hydraulic systems too, it struck me as odd also, but it's to keep the drive motors clean as the Motor oil has a detergent in it. ;)

I will second or third, I might have lost count, Good quality synthetic 20W50 motor oil.
many older tractors used motor oil in their transmission and rear ends. Both Fiat and David Brown for sure as I worked for them back in the stone age! I also worked for a few years repairing hydraulic systems on oil rigs, the ones that used motor oil gave very little trouble! In my opinion motor oil is a very good hydraulic oil and usually is much cheaper too.
 

lugbolt

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ZG127S-54
Oct 15, 2015
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Mid, South, USA
I have used UDT and Super UDT in transaxles (hydrogear) in the past successfully. They're still working to my knowledge. Have also used Super UDT in power steering on my old Mustang. That system runs hotter than SUDT is designed, thus it burns and stinks to high heaven. Went back with ATF. Have also used engine oil (5w20) in automatic transmissions and it works but converter stall speed drops off a little and it's a little sluggish at cold temps. As far as using engine oil for hydraulic? At $5.00/quart (average price for engine oil unless you buy Fred's oil at $1.50/qt on sale), it comes out to $100 for 5 gallons which is more than UDT and more than ISO46.
 

mickeyd

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2014 L3200 DT w/LA524 FEL, 2019 Kubota Z121S w/ 48" Pro Dec, TG1860G w/RCK54TG
Mar 21, 2014
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Guin, AL
Castrol, Valvoline, and Mobil have it too.
What I meant was "having trouble finding someone local that sells it." I can find conventional 20W-50 oil most anywhere.

I tried AutoZone, Advance Auto, Napa & Walmart with no success.

I took Matt's advise and used 15W-50
 
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Quadna71

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Z121S
Apr 16, 2020
8
0
1
Delaware, USA
Hey @mickeyd where did you find the service manual for flushing the fluid and changing the filters? I want to make sure I have torque correct as well as any bleeding steps if/when I do it on my Z121s. Thanks!
 

mickeyd

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2014 L3200 DT w/LA524 FEL, 2019 Kubota Z121S w/ 48" Pro Dec, TG1860G w/RCK54TG
Mar 21, 2014
1,192
17
38
Guin, AL
Hey @mickeyd where did you find the service manual for flushing the fluid and changing the filters? I want to make sure I have torque correct as well as any bleeding steps if/when I do it on my Z121s. Thanks!
I do not have a Service Manual.

In the Operators Manual on page 29 under "Maintenance" It states that the Transaxle oil and filter must be changed at 100 hours and then every 400 hours there after.

On page 53 under "Periodic Service" it shows how to change both.

Thanks for your service. How long were you IN?
 
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lugbolt

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ZG127S-54
Oct 15, 2015
4,807
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Mid, South, USA
I can tell you how to do it, most of the ZT2800 and ZT3400 HST's are identical in servicing.

Remove the filter, oil will drain out-all of it will. That's how you drain them. It comes out fast too so be ready. Replace filters with new ones. Now, at the top, inside of the hst there's an allen head plug. Right in the middle, toward the top. 1/4" allen. If you have an allen socket, great use that if not use a standard allen wrench and pray for it. Clean out the hole where your socket will go in, and grab a cheater because those plugs weld themselves in, and will pop loose when you get enough torque on them, such that they're knuckle busters. There is a plug on each hst. BTW I have broken ratchets when the plug pops loose so you have been warned.

Now you're gonna fill the reservoir and let it continue to fill the hst until oil runs outta the hole u just took the plug out of. Repeat for the other side. It'll take roughly 5 quarts. Once both sides are full, and the plugs are back in, lower the machine to the ground, start the engine and go drive around for a while-to get it hot. Before doing so, make sure the oil level in the tank is about halfway up (which is actually over-full but trust me here). After you drive around a little bit go park the machine for the night, come out next day and look at the tank's oil level. You want it to be at the cold fill line. If it's over full, use a turkey baster to extract a little. If it's dry, add a little and watch the level-it will fluctuate with temperature and after a few mowing cycles it should stay roughly at the same cold level.

If you're doing it without any sort of lift I feel for you.


I have two tricks up my sleeve but won't go into those. It saves a ton of time but requires the "right touch" and secondly a special tool and fitting. Without them, takes about an hour & a half give or take, with them, 20 minutes tops assuming none of the bolts break off in the filter covers. And that's using a lift--without a lift, it's a half day project for most people.

I recently did mine, synthetic because I had it. One thing I noticed is that synthetic fluid expands and contracts a lot more and when the mower is cold the oil level is perfect (cold fill line) and after I mow, it's about 3/4 the way up in the tank. With the old dino oil, it rarely got much more than 1/3 of the way up. If you have a rough yard, and the oil level gets up that high, it can spew a little vapor out and it will make a mess as the dirt sticks to the vapors. Just warsh it once in a while, problem solved. Or use dino oil. It makes no difference. I noticed zero difference other than what I mentioned. It's not any quieter or noisier, no more or less power, not any more or less smooth, nothing. IF I didn't already have it, I would not have used it and just used some cheap kawachem 20w50 that I also had in a 2.5 gallon jug. Saved it for the engines since I am maintaining 3 diesel mowers and then my little gas burning ZG127S.
 
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Quadna71

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Z121S
Apr 16, 2020
8
0
1
Delaware, USA
I do not have a Service Manual.

In the Operators Manual on page 29 under "Maintenance" It states that the Transaxle oil and filter must be changed at 100 hours and then every 400 hours there after.

On page 53 under "Periodic Service" it shows how to change both.

Thanks for your service. How long were you IN?
21 years - retired in 2011.