# Why Is It Necessary To Change Hydraulic Oil Yearly?



## rswojo (Sep 24, 2010)

It seems most plow manufacturers recommend changing hydraulic fluid in their systems yearly mainly to remove water from the hydraulic system.

I own a Kubota tractor with hydrostatic transmission, front end loader and backhoe. Kubota recommends hydraulic fluid changes at 400 hour intervals.

Hydraulics unless leaking are supposed to be sealed systems. Snow is frozen water. Unless the hydraulic system is leaking how is the snow/water getting in there?

What is the difference between tractor hydraulics and plow hydraulics that require this excessive maintenance?


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## clark lawn (Oct 7, 2005)

The oil gets water in it due to condensation (moisture in the air) . It is not 100% sealed as then it would create a vacuum when running tools. I think the reason for the frequent changes on the plows vs tractor is the volume of oil in the system. I quart or two compared to a couple gallons.


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## rswojo (Sep 24, 2010)

clark lawn;1630738 said:


> The oil gets water in it due to condensation (moisture in the air) . It is not 100% sealed as then it would create a vacuum when running tools. I think the reason for the frequent changes on the plows vs tractor is the volume of oil in the system. I quart or two compared to a couple gallons.


I get your point. Actually it is a quart or two compared to about 16 gallons.

Thanks.


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## dieselss (Jan 3, 2008)

Dirt and debris in the plow systems. And more prone to water in the system
In both the systems theres a pump that squeezes the fluid to get psi. Eventually you will break apart the fluid on a molecular level and the protection its supposta provide internally in the system won't he there. Now up to you if you choose to change the hydro fluid in the tractor. But the plow,,,cheap insurance to do it once a year


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## Big Dog D (Oct 1, 2005)

It helps with their annual sales.


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## rswojo (Sep 24, 2010)

> Now up to you if you choose to change the hydro fluid in the tractor.


Of course I change my hydraulic fluid in the tractor. I wouldn't even want to imagine what a hydrostatic transmission or a Kubota hydraulic pump would cost.

Ok, let's switch gears a little. I plow my own 600' driveway, that's it. This winter we had snow often and the plow got used more than normal. Last winter we had a very dry winter and I used the plow a half dozen times at most, if that. After a dry winter with such little use would I be able to skate a little and skip the yearly change?


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## dieselss (Jan 3, 2008)

What about the plow just sitting in the summer. Hot and cold humidity etc. Me personally,,,I'd change it its no fun heating your resivor during a blizzard cause it froze up.


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## Big Dog D (Oct 1, 2005)

What is the difference between your plow pump/resevoir and say the one on your backhoe, bobcat, lawn mowers, etc pumps and resevoirs that sit dormant for long periods of time?


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## dieselss (Jan 3, 2008)

Really no different. But anytime its electric over hydro you always run the risk of excessive amp draw. 

The equip hydro usually always run as soon as you start them or engage PTO and you have an engine running it. The engine hydro usually runs hotter so if there is a little moisture it can burn it off 
But any system runs the risk of moisture into it


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## tuney443 (Jun 25, 2006)

rswojo;1630687 said:


> It seems most plow manufacturers recommend changing hydraulic fluid in their systems yearly mainly to remove water from the hydraulic system.
> 
> I own a Kubota tractor with hydrostatic transmission, front end loader and backhoe. Kubota recommends hydraulic fluid changes at 400 hour intervals.
> 
> ...


There is NOTHING excessive here--it's called PM or preventive maintenance and it's equally important as changing your engine oil and filter.

Hydraulic systems,as already noted are venting to the atmosphere,thus they can and will bring in water from condensation.Water,as you can imagine is harmful to pumps and valves--the longer a rig sits idle,the more water enters the system which is the primary reason why besides hours,you also have to change the oil regarding time--ie:1,000 hrs.or every 2 years,whichever comes first.

Now we also have debris--metal shavings from pumps and the bores of valves,seals and O rings deteriorating,and dirt sometimes from being careless when topping off the tank.All harmful in the long run,sometimes even sooner if a large enough piece enters a valve bore and prevents that function from working.This is why most manufacturers want you to change the hydraulic filter at half the time/hours of a fluid change.

Lastly we have deterioration of the fluid itself.Just like engine oil,heat and time will deplenish the additive packages in the hydraulic oil rendering it not being able to fully do it's job.

Quality of oil is equally important--NOT ALL HYDRAULIC OILS ARE THE SAME!!! Huge differences out there--I've even seen ''comparables,will fit'' oils destroy trannys and internal wet brake systems.Best to either stay manufacturer brand or do a THOROUGH research,NOT asking the pimple faced kid at Walmart.Having said that,if you go to a premium synthetic hydraulic oil such as by Schaeffer,you usually can double your oil's life with a scheduled oil analysis program.

Hope this clarifies.


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## rswojo (Sep 24, 2010)

tuney443;1631072 said:


> There is NOTHING excessive here--it's called PM or preventive maintenance and it's equally important as changing your engine oil and filter.
> 
> Hydraulic systems,as already noted are venting to the atmosphere,thus they can and will bring in water from condensation.Water,as you can imagine is harmful to pumps and valves--the longer a rig sits idle,the more water enters the system which is the primary reason why besides hours,you also have to change the oil regarding time--ie:1,000 hrs.or every 2 years,whichever comes first.
> 
> ...


Crystal clear now. Thanks for taking the time to write the long informative post.

BTW I use genuine Kubota oil and filters for my scheduled maintenance on the 3130 tractor/loader/backhoe.


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## MickiRig1 (Dec 5, 2003)

Every time you move a cylinder that is exposed to air you get a little amount of water in the system. No doubt with plow rams and lift cylinders. The vent air brings in a little too. leave the oil set in a drain pan a few days. You will see the water separate out.


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## MickiRig1 (Dec 5, 2003)

I see it all the time. Water is everywhere.


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## tuney443 (Jun 25, 2006)

MickiRig1;1632324 said:


> Every time you move a cylinder that is exposed to air you get a little amount of water in the system. No doubt with plow rams and lift cylinders. The vent air brings in a little too. leave the oil set in a drain pan a few days. You will see the water separate out.


Unless your seals on the rod end of your cylinder are worn or ripped,water is not coming in there.If that was the case,excavators that dig ponds and do dredging work would need their fluid changed constantly.The venting brings in condensation in very small amounts which over time can be significant.


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## peteo1 (Jul 4, 2011)

Tuney is right. As long as your seals are good you'll only have to worry about the vent. FWIW, I can't recall ever changing plow fluid. I ran an ez vee for about ten years and the only time it got new oil was if a line broke. Never had any issues with it. I'm not saying its the right thing to do but I've never had any plow problems due to bad fluid, maybe I'm just lucky.


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## rswojo (Sep 24, 2010)

peteo1;1632438 said:


> Tuney is right. As long as your seals are good you'll only have to worry about the vent. FWIW, I can't recall ever changing plow fluid. I ran an ez vee for about ten years and the only time it got new oil was if a line broke. Never had any issues with it. I'm not saying its the right thing to do but I've never had any plow problems due to bad fluid, maybe I'm just lucky.


That's why I was asking. My old Meyer was new in 1978. I bought it in 1987. I don't know if the fluid was changed regularly or at all before I bought it. I ran it until 1996 when it started leaking. I took it in to a shop and had a complete seal kit installed and it got new fluid. I then ran it until 2011 when it seemed to have trouble lifting. I took it in to get it tested/repaired. They installed new fluid and it tested to specs OK.

If the system leaks it will suck in dirt as well as water. They Meyer E47 was neglected and it really didn't seem to hurt it. I didn't get a manual with it so I did not know yearly fluid changes were recommended.

I logged for a living for a few years and when the logging trucks showed up to transport our pulp and logs they were always leaking pretty bad. I commented about the leaks to one of the truckers and his comment was: "If it isn't leaking something is wrong".


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## MickiRig1 (Dec 5, 2003)

The 2 plow trucks I have owned both had new angle cylinders and rebuilt pumps. You figure, when we actually did get real snow events in the past. The trucks would be working 100 - 150 hours a season. Figure how many times you lift or angle an hour. Even if your getting 15 molecules of water each time. You still end up with 3 table spoons of water a year. Plus a small amount of seal debris and pump metal. It just makes sense to change the fluid every start of the season. I think it's cheap insurance. No freeze ups, or no moves. Less wear potential.


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## tuney443 (Jun 25, 2006)

Should be part of every plow's PM program once a year including cleaning the pickup screen.


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## basher (Nov 13, 2004)

The more the plow runs the less problem contaminated fluid is. The more it sits the more issues you will see. Valves stuck/rust, ports clog. Leave your vehicle sit for 6 months and head off for track day and see how well it operates. Synthetics say they have 100K mile lubrication abilities, why doesn't anybody just change filters regularly and top it off for the first 100K? If nothing else it's piece of mind when the temps are in the teens and the snow is falling. That's when you stop for a bite to eat or a coup of coffee and the plow is slow or lifts part way and stops when you get back in the truck. Then you stick it on the passenger's floor and let the heater blow till it thaws, bolt it back on and work till she freezes again.


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## MickiRig1 (Dec 5, 2003)

But, I am crazy because I change the fluid and clean the filter screens every year! How much does that fluid cost? What do you make an hour?


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## Antlerart06 (Feb 28, 2011)

rswojo;1630852 said:


> Of course I change my hydraulic fluid in the tractor. I wouldn't even want to imagine what a hydrostatic transmission or a Kubota hydraulic pump would cost.
> 
> Ok, let's switch gears a little. I plow my own 600' driveway, that's it. This winter we had snow often and the plow got used more than normal. Last winter we had a very dry winter and I used the plow a half dozen times at most, if that. After a dry winter with such little use would I be able to skate a little and skip the yearly change?


In a Ford tractor cost 13,000

Over the years I notice If I park my truck in the heated shop My plows would show more water in the fluid vs plowing and they park out side I still drain them all but signs comes from ones park inside Going from cold to heated shop creates condensations


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