For my 5c worth (they don't make 2's anymore Drak
) my theory is to use any good quality name brand concentrate and dilute it to suit your needs, but always get a little bit more than you need and keep the spare in the shed. That way, when you need more (and you will at some point) you can top it up with the same stuff. If you get the concentrate, it's easier to store and you can play around with the dilution a bit. For instance, my Moke runs very hot in summer, but is also subjected to frosts during the winter (Usually in the shed, but I'd rather be safe than sorry and have it covered in case it gets caught outside one night) so I run a fairly high concentration of coolant to both protect against freezing and boiling - very cheap insurance for the little extra coolant you use in a Moke system.
Not mixing it is quite important though I believe, and as I'm not a chemist and don't fully understand which types are compatible with which, I figure the safe bet is to use the same brand/type all of the time. I've gradually brought in a system of running all of my vehicles on the same coolant to save confusion and cut down the likelihood of confusion. Also cheaper as you only need one spare bottle of concentrate in the shed. The tricky bit is to remember to tell the mechanics which service my moderns about the system...
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