I personally would not use the name brand stores fluids for hydraulics..They are very cheap ..Make sure what u buy it says Premium on it any way...I would say no less than 60 to 70 bucks for 5 gals. To start out for price..Im willing to pay the price for as theses systems or machines are not cheap themselves...I don't understand how or why some have no problem spending 25 to 50 grand on the machine but then wont buy a good product for the equipment to maintain it...
i used dte light in many hydro system. my freind has a source of the stuff. i use it because its free. I use cheap farm supply chain, then walmart supertech as runner up.
ps kubota dealer i bought my 2004 rtv-900r from serviced everything with kubota udt "service pro universal trans/hydro drum" I have use supertech universal tractor since 7.5hrs. i have 1400hrs no problems, other then shocks and cv-shafts in front(a boot went bad)at 1000hrs.
i have a 630 that had a onan repower. i used the same as above, tsc universal tractor. engine is very tired and i am looking for a wisconson to put it back to origanal. i changed the filter every 150hrs and fluid every third filter. i put around 1600hrs on it so far. other then a hose or two i have had zero hydro problems.
"The manual says to use Bobcat part number..."
What's the number? Throwing that puppy into Google and see what comes up should be one step -- you can see what that oil's all about, then look for those qualities/specs/viscosity in a replacement oil.
I think you're right that ISO 46 is right for the Bobcat hydraulic components. Just make sure you get a quality anti-wear hydraulic fluid (Unless it is really cold, then get a multi-grade). You could probably use a universal tractor oil, too, just try not to get the cheap stuff - beware the slop oil.