Cost Effective Maintenance produce a cooling system treatment called RMI- 25. They say, water provides more efficient cooling that the common gylcol type coolants, which are not necessary under typical Australian conditions. Waterless coolants are generally pure glycol, and your engine will run hotter!!
RMI-25 cleans and cools by 7c or more. I've recently ordered some to try it out.
http://costeffective.com.au/product/...tem-treatment/