I know that Tom and Ray have said in the past that you can mix coolants, but I have been on a forum that had an individual make the following statement about coolant:

Tom and Ray usually know what they are talking about, but this time they made a mistake. There are basically THREE types of coolant. One, “OAT” has “organic” additives, “IAT” has inorganice, and “HOAT” has a “hybrid oraganic additive technology”. IAT is the classic Prestone and is usually green. The inorganic is silicate, and it protects metal surfaces from corrosion. But some manufacturers wanted something better for engines with a lot of aluminum, so they developed “OAT”, which didn’t work very good when it first came out in the 1980s. Now it is all better. But because silicates work so well, some cars use the hybrid, which has just a little silicate, and also the organic additives. It used to be easy, because European cars used one, American cars used another, and Japanese cars used the third. (Mercedes and BMW use blue coolant sometimes) But now it’s hard to identify which one to use, and the manufacturers sure don’t help by putting all the info on the label. Sure would be nice if every owners manual came with a list of approved products. Or maybe they could post it on line, so it would be easy to update.

I am just wondering if this is true…and if so, should you purchase only the OEM coolant, or is it okay to use the old standard “prest___” type?