The Shell Rotella HD is awful in colder temps and was basically unusable in MN winters. I swtiched to full synthetic Lucas "Universal Hydraulic Fluid" and it has been outstanding so far.
Here's the Lucas fluid at a great price: Lucas Oil 10100 Lucas Universal Hydraulic Fluid | Summit Racing
Here's my thread that has some other synthetic options too: Low temperature hydraulic fluid?
Here's the Lucas fluid at a great price: Lucas Oil 10100 Lucas Universal Hydraulic Fluid | Summit Racing
Here's my thread that has some other synthetic options too: Low temperature hydraulic fluid?