Had the car in for service last week, and the garage spotted it was overdue for a coolant change (good), so they put in bog-standard blue stuff (bad). I spotted this ASAP, and asked for it to be changed but since the garage reckoned it wasn't their policy to use G12, I had to get back to my house and get some of my own. No big deal - I'd not long got a big bottle of Eurocarparts' TL 774D (i.e. Audi's name for G12) concentrate, so I had plenty to spare, and once I got back they said they'd drain the blue stuff, flush the system and fill it back up with my red coolant. And when I picked up the car, it looked as though they had, so apart from having to fill time for a couple of hours. I was happy enough.

But then I got home, and the expansion tank was full of PURPLE liquid:

I was fuming! To me, red coolant + blue coolant = the purple stuff I had now!

So I went back the the garage - rant rant rant, never coming here again, want money back, rant rant rant. Garage wouldn't budge, though. They said they'd done everything I'd asked, and it must be the coolant I gave them. More ranting and raving, but I was getting nowhere and went home to dig out my Haynes.

Anyway, I didn't need the car again that day, and so I went back the next morning, and was ready to start work when I was presented with an expansion tank full of PINKY-ORANGE coolant:

I was HUGELY CONFUSED:

...but still worried, with my head filled with tales of brown sludge (which I've circulated myself on here, I must admit) and all sorts of other horrors. So I started the engine to see what would happen, and while I waited for it to get warm, I did some research. All I could find was this:

http://www.filtercouncil.org/techdata/tsbs/05-2.pdf

...which reckons that, other than losing the long-life properties, mixing anti-freeze is actually OK. Any warnings of bad reactions seemed only to be listed on forums and chat-rooms, so I was starting to wonder whether the sludge formation was a 'fact' like swallowing eight spiders per year...

Once the engine was warm, I decanted some of the was-pinky-orange-now-purple coolant, put it in a jar and left it to cool. Just in case the stuff was separating as it cooled down, leaving just the orange stuff in the expansion tank. But no, it went orange over the next couple of hours, too!?!

Anyway, I'm having the water pump changed next service, so I reckon I'll stick with what I've got in there for the time-being in light of the Filter Council article. But I'm still wondering WTF is going on...!!!

You have no need to worry. The purple stuff will be G12+ or G12++, both are compatible with the pink G12. It is the Blue/Green (G11) stuff that you must not use.

I have found this pic on a passat forum that makes it clear.

Legend:

G11 green-blue

G12 red

G12+ and G12++ purple

Taken from here http://forum.vw-passat.pl/showthread.php?t=48192 (post #8)

The Purple stuff is newer (G12++ being the newest) and better than the pink G12 coolant.

Edited 14 September, 201015 yr by Jim H

I don't get why the colour changes depending on whether the engine's hot or not, though! From that link you posted, it looks like it depends on what the bulk coolant is as to whether you can add the different coolants to them?!?