I have a Snorkel/Economy Wildcat 1200 Series Self-Propelled Work Platform (Scissors Lift). The operators manual states that "10W-40 Hydraulic Oil, 320 sus @100 deg. F., pour point of -35 deg. F." is to be used in this unit. When I tried to get some oil locally the countermen acted like I was crazy saying essentially, "Hydraulic oil doesn't come in multi-weights, only single weights. If you want multi-weight just use 10W-40 engine oil". I purchased the unit used and it only has ~80 total operating hours so I'm assuming the oil has never been changed. What would be the reccommended brand(s) and type(s) of oil to use in this equipment?