I'm pretty sure I had only used G12 prior. I bought the Prestone 50/50 "goes with everything" coolant because my coolant light had come on. I remembered not to mix colors as soon as I started pouring it.

Should I flush the whole thing? Can I just continue topping of with G12 or distilled water? The level is way below the minimum line.

  • How much did you actually add @NilsGuillermin? A small trickle? A few liters? Amount is important. – GdD Nov 26 '18 at 9:34
  • @GdD I poured for about three seconds. Not enough to top it off at all it’s still way below minimum. – Nils Guillermin Nov 26 '18 at 16:06
  • 3 seconds? Don't worry about it, just get the pink stuff and top it up. I'd be looking into why you're losing coolant personally. – GdD Nov 26 '18 at 16:19

Mixing coolants in newish VWs is problematic, as combining the stock G12/G13 pink coolant with green other-manufacturer coolant can lead to the formation of thickening and sludge within the engine's coolant passages.

If you plan to keep the car, you should drain, flush, and refill.

  • I'm not doubting you @David, but I'd be interested in seeing your sources on that. – GdD Nov 26 '18 at 9:35
  • @GdD I was the original owner of a 2001 B5 VW Passat, and I hung out on passatworld.com. There are lots of threads there on what happens when coolants are mixed. I used only G12/G13 in mine; when I sold the car last spring after eighteen years, the cooling system was sparking clean internally. This page has a more scientific explanation: quora.com/…. Perhaps some "universal" coolants would be OK, but I thought using them not worth the risk. – David supports Monica Nov 26 '18 at 19:23

Prestone specifications state that its' patented unique formula is compatible with all other colors of anti-freeze. While I think they wouldn't make a statement like this likely, compatible may not mean it is the best choice. I would have no reservations of using Prestone to top off the system. If I was doing a complete flush and refill I would use the factory recommended product. It is possible that it contains special additives the manufacturer has determined increase the reliability and durability of the cooling system.

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