its also for iron eng with aluminum head combinations because particles from the iron block like to eat at the aluminum. (so to speak, the electrolysis thing i think) but i have the ls1 so i'm not worried lol i use the green stuff. also i you want to use the green stuff and wanna make sure your ok. use a bottle of red lines water weter it has the stuff in it for iron and allum engs and it helps cool. i read a little article on this i can't remimber it all but thats basically what it said the dexcool was for. i think it also goes back to when gm started useing alluminum and pastic radiators they had bad problem with them leaking. betwean the iron and allum and tap water it was killing the radiators. so they made dexcool and use distiled water problem solved. again this is what i found when i wanted to make sure it was ok myself.