I agree, i use 15W40 in mine and am starting to use 20W50 as its cheaper. Any standard engine oil will work just fine in the hydraulics and chain case. Don't use oil for really modern cars as some use really light oils. Stick between 10W30 or 20W50 range and you will be fine. If you run tracks you need special synthetic oil for the gear boxes.
Stephend, (or Steve?), Knowing that Bobcat wants top dollar for everything else, I shopped around for filters. I found Bobcat was no more expensive than the Checker, Napa, CarQuest aftermarket suppliers, but it was pretty clear to me looking at both types of filters that the Bobcat quality was far superior. A couple of examples from two years ago: fuel filter 6667352 $12.36, CarQuest CFI 86192 $20. Engine oil: 6661011 $7.53, Carquest CFI 85083 $7. Hydraulic oil 6661248 $30.56, CarQuest CFI 85455 $40, Napa 1455 $37. So I just get a handful when I'm in the Bobcat store for something else. I've also seen some good deals on ebay, but you have to watch regularly to snag them. --- As for the smaller in-line hydraulic fluid filters, mine (there are two) are in aluminum cases about 1.5" dia and 3" long. The replacement filters are $19 from Bobcat (Tazza will tell you that you can easily clean the old ones, especially if they're not too gunked up), and the entire new assembly (I certainly don't advocate replacing the whole assembly) is $30. And the replace interval on these is I think about a thousand hours unless something goes south and puts a lot of detritus in your system, so the per-hour cost is low. ---Bob