Hydraulic fluid question

My Turf I believe is similar to yours and it calls for the 20w50 oil for hydraulics. I am filling in for the normal mower guy and I accidentally put SAE 30 oil into it for hydraulics. About a half court. Should I be worried about that? What should I do?

snipped-for-privacy@ocacrusaders.com fired this volley in news: snipped-for-privacy@googlegroups.com:

Well... it depends upon the capacity. My hydraulic reservoir is right at

5 quarts. Half-a-quart of 30W oil in there wouldn't hurt a thing, so long as the rest was the right viscosity.

However... another point is that 20w50 "averages out" about 35w... so it probably wouldn't matter much if you put ALL 30w in there!

With hydraulics, so long as the viscosity doesn't diminish TOO far, the major issue is lubricity. Good 30w oil lubricates as well as 20w50 does.

Temperature is your 'proof point'. 20w50 (purportedly) never gets thinner than 20w when hot, and never thicker than 50w when cold. 30w hits that at about the middle -- and modern engine oils (even when used in hydraulics) don't tend to lose their characteristic viscosity for a LONG time.

LLoyd

That's not quite how it works. First, I can't imagine that 20w50 is recommended for hydraulics, unless they run hot. It makes no sense within a sensible range of temperatures..

20w50 is 20-weight oil, period. The viscosity modifiers don't really change the viscosity. They change a viscosity-related performance parameter, but they don't change the actual viscosity of the oil.

You can find detailed explanations around the web, but those modifiers are polymers that swell up with heat. They increase the oil barrier thickness when they get hotter, until the gaps are equivalent to some higher viscosity grade of oil -- in this case, 50-weight. That's the performance parameter they change; not the thickness of the oil itself. It's still 20-weight.

No lloyd - you got it wrong. 20W50 never gets thicker than a cold 20 when cold, and never gets thinner than a hot 50 when hot. That hot 50 is still a lot thinner than the cold 20, which is thicker than a hot

2. A multigrade 20W50 is in fact based on a 20 weight base stock (or very close) with a long chain polymer viscosity improver that keeps the oil from getting thinner as quickly as it heats up .

20W50 is the recommended oil for many hydrostatic power transmission systems, such as the drive unit in many John Deere lawn and garden tractors, and many ZTR mowers.

They DO change the hot viscosity of the lubricant. You can call symantics if you like - the "oil" is what you pour out of the "oil can" and it contains the polymer additives as well as the "base stock" oil. For all intents and purposes the mixture is OIL - and the viscosity of that OIL mix does not decrease as much under heat as straight gerade 20 oil., so 20w50 oil at 200F is significantly higher viscosity than sae20 or sae20w oil at 200F.

There is even a difference in cold viscosity between SAE30 and SAE30W

At 100Ca SAE30 and a 10W30 oil are the same basic viscosity., but at

-30F the 10W30 flows like a 10 weight at -30F.

Straight 30 weight oil is tested only at 100C /212F. A 30W oil is also tested at -30 or -40 and is certified to meet a specified cold oil flow spec which a straight 30 is not tested for (and most likely would not meet).

So how hot does it get? I'm not very familiar with hydraulics, but the higher value in multi-vis oils generally is its

Oh, boy, here we go. In an engine, the mixture could be considered to be the oil. The dynamic and kinematic measures of viscosity in multi-grade oils are based on behavoir in rotating engine bearings.

You're no doubt familiar with the two measures (values of centipoise and centistoke). They're really measuring two different things. There is a misconception that the flow rate under gravity (centistoke) value is the same for a 50-weight oil at 100C as for a 20W-50-weight oil at the same temperature. Not so.

From "Polymers as Rheology Modifiers," G. Ver Strate and M. J. Struglinski Polymers Group and Paramins Technology Division, Exxon Chemical Company, Linden, NJ 07036

"The basic principles of "viscosity modification" of lubricating oils by high molecular weight polymers is discussed. The Newtonian viscosity-temperature characteristics of the oil are not strongly affected by the polymer. The use of polymers simply permits low viscosity basestocks with good temperature characteristics to be employed."

That isn't much of a discussion, but the full paper gets into it. The viscosity-temperature of the oil mixture is closer to the base-oil viscosity index than to some supposed equivalence to the modified oil. The oil is still 20-weight oil. The mixture gives the high-temperature shear strength of a 50-weight oil. And those ratings are based on rotating machinery, particularly automobile crankshafts.

If you don't agree, I'll let you have the last word. I haven't studied rheology and tribology since...jeez...maybe 1980, when I was writing more about engines. But that is the discussion I've had with oil experts.

Here is a picture:

The 10W30 oil still thins as it heats up, just not as much as the straight grades.

...

I'd be awfully surprised to find any that would recommend a 20W50 engine oil for the purpose; certainly I'm certain no Deere recommends anything except J20D Hy-Gard or similar which is

"Hy-Gard and low-viscosity Hy-Gard transmission and hydraulic oils are unique oils developed by John Deere engineers to meet the exact needs of John Deere machines. Both Hy-Gard fluids are multi-viscosity fluids with high-viscosity index. Low-Viscosity Hy-Gard has an ISO 32 viscosity grade. Hy-Gard viscosity places it between ISO 46 and 68 grades. Both Hy-Gard fluids are multi-viscosity fluids with high-viscosity index. Low-Viscosity Hy-Gard has an ISO 32 viscosity grade. Hy-Gard viscosity places it between ISO 46 and 68 grades. Hy-Gard may be used in many applications specifying either of these grades. Low-Viscosity Hy-Gard has the same performance specifications as Hy-Gard and can be used as a replacement for Hy-Gard in cold weather."

On the comparative chart of ISO vis a vis SAE, this puts it at the very, very bottom-most end of the 20W50 range; the SAE20 range is far more typical for hydraulics for anything and everything I've ever run across from the JLG manlift to Deere from the little ZTR to the "big iron" tractors, combines, etc., etc., etc., ... Paint color makes little difference altho Case-IH, Cat, NewHolland, etc., etc., etc., all have their own slightly different spec's.

Every once in a while one runs into a very specific machine that has it's own particular needs, but in general can't go wrong w/ one (altho don't want to mix 'em). That'd be my main concern in OP's case here, far more than just the viscosity altho again it'd have to do a lot with what is the capacity as to how much is foreign in the total. Since it's not his machine and he's in the position of the expert, my personal opinion is he ought to bite the bullet and correct the error for the customer, just on general principles since he knows he screwed up.

My little Poulan Pro with a HydroGear tranny calls for same, 20W50 engine oil. The repair manual has:

=== Table 3. Fluid Volumes for the 310-3000 IHT Fluid Description: 20W-50 engine oil Volume: 0.95 gal. (121.6 oz) (3.59 liters) ===

I pulled this out of a 2014 Exmark Lazer manual:

=== Exmark Premium Hydro Oil is recommended. Refer to the chart for an acceptable alternative:

Hydro Oil: Exmark Premium Hydro Oil (Preferred) @ 500 hours Alternative: Mobil 1 15W50 @ 250 hours Hydraulic Oil Capacity: 5.5 qt. (5.2 L) ===

Sorry, I accidentally deleted the rest of that sentence, which was...

...equivalence in terms of its ability to avoid shear puncture in a rotating bearing. It is not necessarily (except with synthetic oils) the same thing as its flow rate under gravity, which is the kinematic measure of viscosity.

Huh. Guess that's what one gets for having green and red paint; never seen such...the old Chebby trucks used to spec straight 20/20W and Dad wouldn't ever let us even wave a multi-grade can near one of 'em! :) I still have and use the '58 C60 283ci as seed tender and keep one 30 gal drum of 20/20W just for it so his ghost won't come and haunt me!

Meanwhile, for nearly 40 year ran Co-oP "Circle 3" in everything else on the place including as both engine and transmission/hydraulics. So, I guess in thinking back, that was actually moderately close; I'd have to go back and look up what its SAE designation was--since it was universal never really ever thought about it, just put it in everything _except_ the Chevy's! :)

Finally with the "Tier X" had to go to the higher performance engine oils for the diesels so now have to stock both it and the hydraulic oil. We use enough on the farm so buy both on bulk basis thru a local distributorship.

Ed Huntress fired this volley in news: snipped-for-privacy@4ax.com:

Well, then Ed, I think you have ZERO experience with commercial hydraulically-driven ZTR mowers.

I'd suggest you educate yourself before condemning something you know nothing about. L

snipped-for-privacy@snyder.on.ca fired this volley in news: snipped-for-privacy@4ax.com:

Yeah, actually, you're right. I swapped the issues.

But Ed Huntress's input was pure bullshit propelled by a sense of self- importance!

Lloyd

So why don't you educate me, Lloyd? Why do they recommend an oil, the design purpose for which is to lubricate rotating machinery (primarily IC engines) at high loads and over a temperature range of 0 to 100 deg. C, for hydraulics? Why not a hydraulic oil, which generally is made from a higher VI base oil and contains different additives for corrosion protection and for piston lubrication?

I'm all ears.

On 06/17/2016 4:48 PM, Ed Huntress wrote: ...

I'd guess for two reasons --

1) Cheaper and readily available vis a vis a proprietary hydraulic oil for their specific purpose, and

2) That ZTR usage as well as other hydrostatic transmissions, etc., really is a bunch of rotating parts and all, not actually cylinders and such.

I did look up and discovered that Bad Boy ZTRs all spec 20W50 engine oil. As noted before, the Deere ZTR I have uses the J20D by spec; it'd _probably_ do as well on the other as well but I'll just stick with the spec.

As I noted in another earlier response, hadn't really thought about the viscosity range but we ran the Circle-3 in everything from small equipment engines thru the LP-gas fueled to the largest diesels tractor/combine engines as well as the hydrostatic transmissions (which same reservoir also served the conventional hydraulics as well) without an issues on a whole range of manufacuters--from Allis-Chalmers to International Harvester Farmall to Case to Deere with a little Massey and a few other odds 'n ends to boot for 40 yr or so with nary an engine or transmission problem so in general there really can't be too much that specific about the oil vs the equipment manufacturer.

It's only when there's an issue of potential repair/warranty work that one gets worried about being covered if something bad _were_ to happen. With the Circle-3, the Co-oP warranted anything it was used in with only one caveat that you took and sent in the oil samples every change and kept to the scheduled change period. I never heard of a failure and Dad was president or on the Co-oP board for 20+ yr of that time and they consistently had interaction with the refinery R&D folks who kept making tweaks to formulation to keep up with changing demands of the newer equipment.

If you're going to start that kind of shit, Lloyd, let's get into your recommendation, which was full of errors and the reason I responded in the first place.

Bullshit. It doesn't "average out" to anything. It has one set of properties at low temperatures, and another at high temperatures. If you dilute the viscosity modifiers in 20w50 with single-viscosity oil, you don't know what you're going to get except a dilution of the viscosity modifiers. It happens that an equal mixture of two multi-weight oils has a low-end viscosity closer to the lower one of the two, not an average, but you can get away with mixing two multi-vis oils.

That depends on the operating temperature and the kind of bearing shear you're dealing with.

Aside from getting that first part backwards, 20w50 is 20-weight oil with modifiers. The modifiers have to be in the right concentration to work. You don't get something "in the middle."

There is a lot of contradiction among oil suppliers about the effects of mixing oils of modern multi-vis types for an automobile engine. Most say you can do it. But it's because they're all using pretty much the same modifiers today. There are no viscosity modifiers in single-weight oil.

This sounds something like your "aluminum burning in air" story. You think you know something, but you really don't. Rather than take off on an ego trip you might want to discuss the subject first.

Whatever works. I'd just be wary of doing much mixing of types. They don't "average."

On 06/17/2016 5:51 PM, Ed Huntress wrote: ...

I agree wholeheartedly on not mixing; as noted elsewhere that's the only real concern I'd have on the OPs query that the two aren't as miscible as one might like or that one's additives don't "play nice" with the other's...for a small, low-temp, pretty low-stress application, likely won't make a lick of difference, but "ya' never know" and Murphy does seem to hang around a lot...