you should only use distilled water. Water Wetter didnt do much good in my Defender, I figure it cant hurt go for it. In my Classic I used a whole container of the green antifreeze water wetter and topped up with distilled water. I have a recored radiator a 180 thermostat and with the VDO gauge I sit on the 180 mark or a hair below, with the infrared gauge I am between 180 and 187.