Just bought a used car. Coolant question

2006 GMC Envoy
I have no clue what sort of coolant (dex-cool or generic) is in there or how long it has been in there. Should I just bite the bullet and have it flushed or is there a way to tell how long it’s been in there (old vs new) and what type is in there since color is no longer an indicator.

If you’re not sure just do it. For less than $100 you can have peace of mind. Just make sure you use the right stuff to replace it and properly get the air out of the system when you’re done.

I agree with the above, just do it right and you should have many worry free years about it.


GM still uses Dex-Cool across the board today. There never was anything wrong with it as a coolant, the problem when they first started using it was an incompatibility with some of the sealing materials in the then current engines. that was solved well before 2006. pretty much the entire industry has moved over to organic acid tech (OAT)-based antifreeze.

here’s a cheat sheet: http://www.eastcoastrollingthunder.com/temp/antifreezecolor.jpg

There are labs that will analyse coolant to check for corrosion, effective freeze / boil point, etc. but I get the impression their services are aimed at owners of huge fleets of huge machines, like construction equipment.

There are also density testers that look like turkey basters with a floating arrow inside.

Or test strips for pH, contamination, & remaining life.

Probably easiest & cheapest just to flush & refill.