I've been looking at this for some time now and I'm not sure what is the best route to go. I am working with a '97 4Runner and Im flushing the cooling system. It currently has green coolant in the system and appears to be clean and in good shape. I generally like to put the original coolants in my vehicles, but I also like the added flexibility of bring able to top off coolants when necessary and I don't always have Toyota coolant on hand. I looked further into this, and I thought I would just get an aftermarket red coolant. Turns out though...the Toyota Red coolant in a hybrid (HOAT), rather than a full on OAT coolant. I have purchased the Peak Asian Red/Pink Coolant in the past, but I just realized they are an OAT, not a HOAT. I don't know the net affect of mixing an OAT coolant formula with an HOAT. Also, I would just use the Zerex Asian Red coolant, but they don't sell it in concentrate and the value is not there for me to use that (even though it appears to be an HOAT also). Any idea what happens if you mix an OAT with an HOAT?