Is the 50% antifreeze specified in Volvo coolant necessary in hot\nclimate? Here in Oz I find it hard to get anything approaching this\nratio of 50/50 antifreeze and water. There is no type C either. Is\n33/67 ok? Also what's the difference between type A, B and C? If I\nwere to mix my own is something else beside Ethylene Glycol and water\nnecessary?