Well let me state "That is what I was taught." Has seem to be proven in my experiance with no troubles arrising in my past 5.5 years of ref. service.Others may disagree.By far am I no expert , many have more exp. In fact I"m sure of it.(upper rt corner) Aside from oils in hoses if you get a situation like that , then a flush through the reclaimer with some reclaim has worked for me. JB is 410 and gets used for bulk reclaim.burn out, ,YJ is 22 and low press.Testo used olny where trusted of not suspect of contamination, on all refs.