When you use a product and need to inquire about what to use for it you do a few things
1 - read the manual and follow it
2 - research on how and why
So - if you want a simple answer to this - if you drive a Honda go to a Honda store and buy their premixed coolant and pour it in, if you drive a hyundai shehzore go to a hyundai showroom (which are all closed now) and buy a bottle of coolant from them (but you cannot as the showroom closed off)
So now you can either throw away the Shehzore because no parts are available or try to find the correct "technical specifications" for it so you can actually keep it working. Which means that you then find out WHY was a certain product recommended by the manufacturer - that involves technical details but you say they are useless - Well I guess then ignorance wins here.
In short, I have read that you run an oil retail business - still you are questioning how much water to add to coolant? Its very basic sense and just for keeping the responsibility clear on the manufacturer side they print the usage of coolant in the owner manual. Now you being in the oil retail industry can easily get the TDS of the products you sell which are a must for a business like yours - Just like when you ask me about these technically I reply to you accordingly - because this is a discussion forum. But you just claimed that you dont need any technicalities just sentences like - buy this and thats all. But then you ask such questions of HOW much water should I add to coolant - This is really sad because on every package it will claim either its premixed ready to use or requires dilution with water and secondly you already are in this business - and in every business you should know the finer details about it - thats how you win.
In very simple terms henceforth
"when buying coolant READ THE PACKAGE" If you cannot understand it, you can take a picture of it and post here with your question"
To answer the water as heat transfer medium question I would need to verify first that you can actually understand the concept of latent heat in thermodynamics