The service manual for my (1988) 843 bobcat says you can use 5W30 motor oil for hydraulic fluid. So my question is, it OK to use a full synthetic or synthetic blend of this oil? What would any pros or cons be? Also, I can't seem to find what type of oil is spec-ed for the ISUZU engine (54 HP 4 cylinder) Anyone know? Thanks!
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OldMachinist
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The question about using engine oil for hydraulic/hydrostatic oil comes up a lot. Bobcat used to say you could use engine oil instead of their oil but a few years ago they said that because of changes in engine oil formulas they no longer recommend it. That being said many owner use engine oil without problems. I use universal tractor transmission oil that meets spec for use in hydrostatic systems.
1ofU
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I use universal tractor transmission oil that meets spec for use in hydrostatic systems
yep same here , get it at my local farm store
SkidRoe
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It kind of makes me wonder if Bobcat's change of heart has something to do with them not selling enough of their own brand hydraulic oil.... I use 10w30 in my machine. Works fine.
OldMachinist
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It has to do with the reduction of Zinc DialkylDithiophosphates in engine oils. The phosphorus in the older formula screws with the modern emmsion systems. The Zinc/Phosphorus is a anti-wear/anti-oxidation additive. Some engine oil companies sell off road use only oils for the racing/classic car people.
Here's the official release from Bobcat Company:
"Bobcat Hydraulic/Hydrostatic Fluid is specially blended for use with Bobcat hydraulic and hydrostatic systems. Bobcat Fluid has been developed to meet the growing demands placed on hydraulic components, while engine oil is designed to meet requirements for use as an engine lubricant. Because of this, engine oil is no longer an acceptable alternative fluid for Bobcat hydraulic and hydrostatic systems. Viscosity. Engine oil viscosity is typically much higher than the acceptable limit of hydraulic fluid. Hydraulic fluid is designed for high pressure applications and with viscosity to operate effectively throughout a wide temperature range. Additives. Bobcat Fluid contains more zinc and phosphorus anti-wear additives than other brands of hydraulic fluid. Zinc and phosphorus adhere to metal surfaces of hydraulic components and act as a coating to separate moving parts. Additives in engine oils do not have the same anti-wear properties. Demulsibility. Under operating conditions hydraulic fluid is designed to separate water, engine oils typically absorb water. Foaming. Most engine oil is not formulated to prevent foaming. Foam is a contaminate that lowers performance, decreases filtration and can cause premature hydraulic component failure."
SkidRoe
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SR's thoughts on this:
I am not going to disagree; there may be some merits to their current oil, but I am more on the page of marketing scare tactics. There are not too many owners out there that have advance degrees in tribology, and Bobcat knows this, so they are going to capitalise on it; just like John Deere, Caterpillar, Cummins, Allison, etc.
To me, a more believable reason for their change in story would be changes to their product line over the years. 20 years ago, BC was pretty much exclusively an SSL manufacturer. Now, they market excavators, UTV's, and compact tractors as well. Having a common hydro/transmission fluid for all of these product lines makes sense. I am willing to bet their current fluid is some formulation of UTF. The anti-wear additive that they are pumping up is likely EPC (extreme pressure concentrate), a common additive in UTF to allow for proper lubrication of hypoid / spiral bevel gears sets found in final drives.
BTW / FWIW - As an aside and with respect to an example of non-mainstream hydraulic fluids being used in hydraulic applications: At work, we have been using Dexron as hydraulic fluid in high-speed, high pressure hydrostatic drives for years with very few problems. Reasons for doing this: cost, viscosity stability, supply base, etc. Yes, foaming can be an issue, but is easily controllable via careful reservoir baffle design. (I am not saying that you should use Dexron this in your BC.)
If what is in your machine today has been working, why switch? To me, it is more important to keep the oil clean and free of contaminants. Change your oil and filter regularly.
My $0.02.
