read the instructions !
I have seen a number of clubs try to save money by watering down Type 2 fluid .
This fluid is ment to be mixed with water but if two much water is used then the mixture re-freezes as clear ice , this is much harder to spot and will add more weight to the airframe than hore frost.
Remember if you have any doubt about the need to de-ice or not to de-ice then there is NO doubt the aircraft should be de-iced !.