Concentrate or ready mixed coolant?
 

so the IMG in the Zed has decided to give up the ghost so I'm going to change it over the weekend along with new coolant which is due a change anyway and I was just wondering whether to get concentrate OAT coolant or just ready mixed OAT coolant. If I need concentrate what is the best ratio for the K-series?

You need to use distilled water, tap water has silicates in it which are not good.

IIRC it should be 50/50.

Once you've bought distilled water it isn't much cheaper to buy concentrate.