I'm about to embark on the 250k service for my '96 Nissan Maxima and part of that service will include a coolant flush. I use Pentofrost antifreeze in all my vehicles-- have had good luck with it, and there's a Pentofrost product to fit nearly every application. Can get concentrate shipped to my door for not much more than a couple gallons of diluted stuff from the store. That said, my research seems to indicate that Nissan used a green long-life coolant in these years, and recommends a 4 year / 60k mile service. Pentofrost A2 is the appropriate coolant, but what is the difference between the red A1 (pre-2004 Toyota/Lexus/Scion), green A2 (Nissan, Kia, bunch of Japanese makes), blue A3 (Honda, 2009+ Subaru & Nissan) and the pink A4 (2004+ Toyota)? All claim to be a phosphated-OAT (P-HOAT) so the chemistry ought to be similar. Is there an advantage to using a newer chemistry coolant (for example the A3, which is recommended for the newer Nissans), and could this possibly extend my service interval if I were to do a complete flush and refill, making sure to fully rid the system of the old stuff? I still have some A3 blue left, as I use it for my Honda Odyssey. Would a switch to the blue (or other color P-HOAT) coolant be of any advantage, or is this a bad idea?