The Shell Lube Finder webpage says the Spirax S4 CX 10W is good for use in the PC78 hydraulics, but checking the 2007 Komastsu operators manual, from -4F to 104F it says to use sae 30w, sae 10w-30, or sae 15w-40 (in higher temps). Oil had changed a lot in recent years and I was wondering if the lighter weight Spirax 10W is now better than the sae oils were in 2007, or should I stick to the 30w or 10w-30 sae engine oil, or go with a heavier Spirax S4 CX 30W. machine S/N is 3377
For the Colorado climate Spirax CX10W will be fine IMHO. Even in tropical climates we still use that same weight of oil in hydraulics. It will definitely help you in the depths of winter when hydraulics are slow to respond.