Right its going to be a cold one this winter.. Ive had 2 water pumps go in the last year and want to make sure the system is good for the winter so im going to do a coolant change , question is how much should i use for the disco ? and what sort? I want to make sure that i get some heat in the cab so dont want it 100% but also dont want to dare run the risk of anything in the pipes freezing? any ideas?