I have an MTD splitter, but the brand matters not - what matters is the pump manufacturer - the hydraulic oil must lubricate the pump. Being lower cost consumer products, many use the Barnes 2 stage gear pump, to 3,000 psi on the 2nd stage. Requirement is 10 micron Beta 1000 (95%), depending how many hours you want to get out of it.
The O&M Manual insists on using only ISO VG 32, app. SAE 10W oil. From back in the day, most gear pump makers spec'd ISO VG 46, so I expect the OEM was spec'ing lower vis for colder weather splitting.