Hey guys I just have a quick question. About a month ago my coolant light came on, so I called the dealer and asked which type of coolant I can put in? so the guy said anything is okay. So my dad had some Prestone (Green Stuff) and I added in about 1/2 litre or so, perhaps less. Now I found out on this forum that I shouldnt use that Prestone Coolant and should use the Orange one or BMW one, Now do I need to completely flush my old coolant out or is it okay just leaving it? and using BMW coolant in the future? thanks!