when i bought my viking the dealer told me to NEVER EVER use any coats & clark thread in the machine---the first 3 or 4 years i didn't---then one day i did---and you know what??? made no difference to anything- worked fine, didn't hurt the machine---made no difference to anything-
try it at home (out of the sheriff's site) & see how it goes- if you have no problem with it & you like it- use it...