thats not a good sign ...
my dads car had the same problem and i guess it was oil mixed twith rad. fluid
not a good thing

 

I think GM recommends Dexcool be changed every 100K or 5 years, whichever comes first. But you can test it with a hydrometer to tell if it is bad. I only did mine at 4 years/50k because it only cost me $14.

 

oh ok mine is going to cost me 85 bucks

 

100K or 5 years is under IDEAL conditions which 99% of people driving NEVER see. You should change it more often if you notice sludge or an increase in operating temperature. I personally don't let and won't let mine go 5 years or 100K miles.