Hi, I use BMW concentrate in my BF @ 50% by volume. I have used it in all my cars over the last 11 years and have never seen anything other than a clean waterjcket at change time. My last car had over 330000km on it with the original waterpump. To changeover I dumped the existing stuff, flushed, then refilled - easy. The best part is that it works out at around $11/1.5l bottle from your friendly BMW dealer and it is blue! The other thing you can do while the system is empty is to fit electrical heatshrink to your coolant hoses to secure/replace the anti chafe sleeves, as I have found that the electrical tape comes off. This is particularly useful on the Boss motors where the top hose runs a little close to the engine cover. Cheers Tom