In the same boat with ya ctfjr, and still need to go pick up a bucket before my chipper (same model as yours) gets here. I spent a bit of time staring at and trying to decipher the secret code in the oil charts, and finally decided that a good premium grade ISO46 oil (not cheap stuff) was the way to go. ISO 46 is relatively easy to find and not too expensive in most cases. Couldn't find any advantage of trying to stay with the same oil used by the HST. That stuff is pricy. You have a single pump turning a single motor with only one restriction (flow control) in the line. That isn't going to generate much heat/oil degradation, even in the heaviest use. Other than water contamination, there really isn't much to worry about, but I would try to keep the chipper covered when not in used. Check the tank often to make sure there's no water in it, because water droplets in hydraulic oil become acidic, and will eat the bottom out of the tank. I seriously doubt the inside of the tank is coated, but I'm hoping Woodland Mills can make a liar out of me. I see UpNorthMI is using ISO46 up there in the Great White North, so I'd suggest the same anywhere in the Lower 48 is a good idea. It's what I'm gonna use down here in the sunny south. Keep your bucket, because that's a vented tank, and you will get some hygroscopic absorption of moisture in the oil, particularly if it sits a long time through cooling/heating cycles. If you can't store the chipper inside, you're probably going to want to change that oil every couple years, depending on how much duty it sees. I'm considering a tank warmer to keep the oil warm in mine while it's in storage.
