So the overflow tank/resovoir was empty so I bought some prestone dexcool and poured it in.

Later when the engine was cool I opened the radiator cap and saw regular green coolant. So it will eventually get all mixed up

So what do ? For snooping around the Internet I read some horror stories of dexcool and suggest to go with pure coolant instead.

I now want to fully flush the system but not sure to go with 50/50 mix of dexcool/water or full antifreeze like Prestone or even their 50/50 premixed coolant.

 

im sure youll get a lot of comments on this one..... i thought the manual said to use Dexcool only.... i dont have it here in front of me though. i agree you should flush it and use Dexcool exactly how it says to.....

 

Follow your manual.

 

ON all the new GM vehicles the green stuff will corrode and eat away at your cooling system that is the reason why they tell you to use dex cool.

 

Flush it out, replace it with the Dexcool. They use it for a reason.

 

According to the DexCool manufacturer, mixing DexCool with traditional green antifreeze reduces the change interval to 2 years or 30k miles, but otherwise will cause no issues.

As far as using straight DexCool, I'd definately change it more often (every two years) than the service intervals in your Owners Manual suggest (5 years or 100k)

There are many reported issues with DexCool not lasting as long as GM prescribes and fouling up the cooling system over time. DexCool is easily contaminated if the cooling system fluid is run at lower than recommended levels. Google search for more info on this issue.



.

 

I have seen them mixed and turn into a nasty brown gelatin like substance, and that can't be good for the cooling system

 

The DexCool has been known to turn into a nasty brown gelatin substance all by itself. Has nothing to do with mixing them.

Here's a couple nice pics of that artifact: Dexcool Pictures

Some more details from that webpage of DexCool issues: Dex-cool Contamination

 

why is dex-cool so controversial dammint!

I'm doing the flush either tonight or tomorrow with a new T-Stat as well (im at 66K) and was going to put Dex-Cool because thats what the manual says and people are here are suggesting as well but now you show me the link above makes me think again!!!!

 

A couple facts on DexCool to help 'cool' your nerves :

1) DexCool is much better for an aluminum block motor due to the lower alkaline content. The higher alkaline of regular green antifreeze is more corrosive to aluminum.

2) The major issue with sludge formation in DexCool is attributed primarily to cases when the coolant level gets too low or when the coolant has become contaminated. Be sure not to let the coolant level get low!!

There are many folks (myself included) that believe that the change intervals suggested by GM for DexCool are too long. I'd change it every 2 years just like regular antifreeze. It's a pretty easy and inexpensive. Better to keep on top of it with shorter intervals than risking it and finding out your system is full of gunk.

The most important thing to do is to regularly check your coolant and radiator for any signs of degradation of the coolant or corrosion in the radiator. Like everytime you check the oil. If it isn't bright orange and clean, change it.