New car! Green coolant in reservoir...

[Pete2B5s]

Hello! This is my first post here, I've owned a 1998 2.8l for about two years and I use these forums often when trying to fix or diagnose problems. Unfortunatly, due to an idiot lady running a stop sighn, that car was declared a total loss, although it still runs great and I still drive it.
Rather than fix the cosmetic damage to that car, I went out and got a 1999.5 1.8t, so far I'm loving it. Lowered three inches, stage one tune im pretty sure, it will hold 17 pounds of boost all day.
Now on to the point of the thread, coolant.

I drove the car about 300 miles home after I bought it, ran great no issues at all.
Driving home the other night, I noticed in town it was running a tick hot, I had done a few hard pulls so I didn't really think much of it, got on the freeway and the temp went back to normal, still driving pretty hard. Few miles before I got home, it flashed a red coolant light on the led screen, the temp was still normal. Got home, checked the coolant and the tank was empty, immediately checked the oil dip stick and that looked normal still. So I parked it, took my other car to work yesterday and bought some g12 on the way home. Filled up the resi with 50/50 g12 and water, drove out to do some errands in the car, temp looked good the whole time doing a few hard pulls in town and at freeway speed, got home and the reservoir was still full, no coolant light for the whole trip. Upon looking closer today, I noticed that the liquid inside the reservoir is actually green in color, where as I know the g12 should be pink. The reservoir it's self isn't in the best shape either I think I need to replace it. So, obviously I have at least a small leak somewhere if I was out of coolant in the reservoir, my main concern right now is all the horror story's I've read of mixing normal coolant with g12.

Any input would be greatly appreciated, what do you guys think?

[Pete2B5s]

I guess my question there is pretty obvious, so here's a better one. How long, if for any amount of time, can I drive the car before I replace the reservoir and do a flush?

[PaperToast]

i would get the old fluid evacuated and the system rinsed as well as possible and refilled with g13, the newer, better coolant, by VAG
ohh, and its backward compatible with all the various g12 versions

[Seerlah]

You can't mix coolants. The green stuff can be used if the system is fully flushed, with all old fluid out. You need to flush that system with water to get all the old fluid out and place in g12 or g13 when done.