I use the NAPA/Valvoline UTF in the blue bucket. 5 or 6 gallons per bucket. Trouble is that the CK30 needs 7 gallons!!!! so I have been storing a partially empty bucket for the last 400 hours of operation.
The CK30 has the main drain and then one additional drain plug below each final drive which is also pretty much the brake housing. The big plug in the middle is the major one though with the magnet.
nappa is about same as tractor supply,well,there you go,thats what to use,be carefull though,they got like 3-4 kinds,get what I said[whatever that was],many words, but its 20 weight I believe,hydro oil is 10 weight,[again I believe].