Hydraulic oil and condensation

If there's a better group to take this question, point me the way. If not, some of you guys have experience with hydraulics.
When I bought my Grasshopper commercial mower with a hydraulic drive 6 seasons ago, the dealer advised me to change the hydraulic oil at 5 years even though I wouldn't have 1000 hours on the machine. The lawn services rack up 1000 hours in a little over a year and change their hydraulic oil almost annually as a result. The manufacturer recommends changing the hydraulic oil at 1000 hours - which will be about 20 years at my useage. It requires synthetic oil and at $16 a quart it will cost about $64 to replace the oil, and another about $14 for the hydraulic oil filter.
I asked the dealer why to do that, and he said he believed that condensation in the oil tank would shorten the lifespan of the components. He said it was his theory that that's what caused some of the problems he's seen, but he stopped short of saying what specifically goes wrong. He felt that it was relatively inexpensive insurance compared to the cost of replacing components.
The machine now has 265 hours on it and is beginning its 6th season. The hydraulic oil has gone from clear to light tan and does not smell burnt. I can see some milky white oil droplets reminiscent of an oil-water mix clinging to the inner wall of the dispstick tube.
Anybody here with specific experience with Grasshopper mowers? Any experience with hydraulics and condensation causing problems over time? TIA
RWL
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<GeoLane at PTD dot NET> wrote in message

If I had evidence of condensation in the dipstick tube, which you do, I would change the oil and filter immediately. A $78 maintenance expense every 6 years is pretty cheap insurance if you compare it to the cost of a hydraulic transmission replacement or rebuild. Water with the resulting rust and sludge is very detrimental to a hydraulic system. It might help dry out the transmission if you run it until it gets good and hot.
Don Young
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GeoLane at PTD dot NET <GeoLane at PTD dot NET> wrote:

Two clues: "light tan" (as in suspended rust particles, probably) and you see condensation on the dipstick tube. Be penny-wise and pound-foolish if you like, or accept that when you bought far more mower than you needed, you bought the maintenance expenses that go with that. Hydraulic fluid should look very close to the way it looks coming out of the bottle at all times, or there are going to be (or already are) problems.
53 hours a year. Poor thing probably never gets adequately warm to boil out condensation, so your "light use" is actually harder on it than proper commercial use, where it would run all day and heat the hydraulic fluid up. You should start hiring out to mow other lawns.
Before you put it up next year, mow for as long as possible to heat it up and dry it out as much as possible.
If there is a vent on the hydraulic system, you might tie a bag of desiccant over that vent when the mower is stored. If there are any filters (fluid and/or vent), change those out, too. Likewise the engine oil.
If you can't find the vent, bag the whole mower up with dessicant.
--
Cats, coffee, chocolate...vices to live by

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I have good friends that have a dealership in them - You bought it - I bought a house for that much years ago - and it was new brick. Cheap insurance at any rate. See if you can buy a 5 gallon jug at the oil company and get a discount. What does it cost in your car or truck ?
Martin
Martin H. Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net TSRA, Endowed; NRA LOH & Patron Member, Golden Eagle, Patriot's Medal. NRA Second Amendment Task Force Charter Founder IHMSA and NRA Metallic Silhouette maker & member. http://lufkinced.com /
GeoLane at PTD dot NET wrote:

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On Wed, 28 May 2008 21:11:54 -0400, with neither quill nor qualm, GeoLane at PTD dot NET <GeoLane at PTD dot NET> quickly quoth:

I change the oil in my truck twice a year whether the mileage is 3,000 between intervals or not. Engines are dirtier than hydraulic systems. If I were you, I'd change the oil at 2 or 3 year intervals for the reasons he gave you. Proper maintenance can extend machine life by orders of magnitude. Just Do It!
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