The recommended engine oil viscosity it 10W-30 (get the heavy duty tractor stuff). That applies to all temperature ranges. I personally have made the switch to synthetic oil, and have been pleased thus far. It has better lubricity, and doesn't break down like conventional dinosaur juice can over time. The final thing that convinced me to switch was that my VW TDI needs conventional oil changes at 5,000 miles, but if you use synthetic, they recommend 10,000 mile intervals.
Front wheel and differential lube is SAE 80W-90. I personally use the synthetic blend here. Also remember there are 3 places in the front end to change oil. The diff, and on each wheel assembly. You have to drain and add to each one. The diff takes 2.1 US quarts, and each front axle gear case hold about 0.5.
Tranny/hydraulic fluid is Kubota UDT or equivalent, approx 19 US quarts. Remember Kubota does not make oil, someone else makes it for them. So you can get any quality (Penzoil, Shell, Texaco, etc) that specifies UDT and it will be just fine, plus you will save some cash.
I happen to have an extra manual I'd let go for 10 bucks plus postage if you are interested. It's in used, but good condition.
