My position is that a flush and fill of $5 Supertech Generic Dex is better than topping off/mixing G-12 and Dexcool. People who are topping one coolant with another are probally overdue for service and simply running it too long. Also, a leaking system that allows air to mix with G-12/Dex is a known problem as far as IT jelling. Low level from leaks>mixing of air into system>topping with Dex>shot cooling system. See the cycle? Nothing to do with them being compatible.
I am just here saying dump G-12 and any unsilicated coolant. In addition to what I wrote below, you all know how long our Audi radiators last, I don't see the same failure rate on Mercedes at my BOSCH Center.
Unsilicated coolants that rely on slow-acting OATs are history, GM and Ford dropped them as well as VW. Lightly silicated Hybrid Organic Acid Technology coolants like Mercedes G-05 have the ability to protect more rapidly in situations where the protective layer has failed due to cavatation, etc. G-05 H/OAT coolant has the longest sucessfull track record, btw. Mercedes' even carries a sack of silicated crystals in the coolant resevior to replenish the silicates. I don't make this stuff up. My theory, after seeing pics in MOTOR Magazine of fully corroded OAT water pumps in controlled tests, is that there are a lot of blown timing belts from water pumps siezed by G-12. There is also the issue of the plasticiser 2-EDTA in G-12 eating through seams and gaskets."
G-12 is obsolete, replaced by G-12 Plus.
[ December 14, 2005, 01:25 AM: Message edited by: Audi Junkie ]