If I remember correctly, in Northern North Sea ops in the UK we got Eurocopter to agree that the criteria for anti icing additive was based on fuel temperature not air temperature. We fitted fuel temperature guages and found that even in deepest winter flying at OAT's down to minus 10deg centigrade the fuel temp didn't drop to less than about +4c. Southern North Sea always had anti-icing additive added to the bulk fuel as the S76 fleet needed it and the majority of the SNS fleet was S76. Don't know what it is like now with all these Italian products around.
Prist is nasty stuff if exposed to it without adequate PPE. If you are a rat your testicles will fall off if exposed to enough of it - allegedly!