well, about two weeks ago i noticed a was really low on anti-freeze/coolant so i got mr lube to top her up. then a week later noticed i was out of coolant again! so i filled her up with some water and dexcool i had in my garage. i then realized my mistake b/c mr lube probably added the green stuff. lately every time i start my car when its cold, it makes a huge scraping/rattling sound from the engine and i don't know if those two things are linked. so my question is should i get my rad flushed and switch completely to dexcool or the normal green stuff?

i have a 2001 v6 auto btw

 

Really doesn't matter which one. GM uses dex. I use "the green" stuff. If Mr lube is not universal then you need to flush and stick to one brand

 

So you got the coolant filled up, and a week later it was out again? Mixing the two coolants is the least of your worries, you need to find out where the coolant is disappearing to. If it's not externally, you have an intake manifold or head gasket problem.

 

yes where did the coolant go? better see what the oil looks like. check the passenger side floor. maybe look at the heater hose plastic connector. mixing the orange and green stuff will not end well either. turns to jello kinda stuff and plugs stuff up.

 

i have checked the oil it seems to be fine. maybe i should check the oil when its cold? and i would have noticed by now if its was leaking somewhere. im so confused as to were its going.

 

stop by the local parts store and rent a coolant system pressure tester. pressure the system up and find that sucker.

 

If the coolant isn't getting out, then it's going in. If not into the crankcase, then it's getting into a cylinder and steaming out.

 

Are you smelling any coolant when you get out after driving. Mine was leaking and it was not visible. Once pressure tested it was the intake gasket and the plastic elbows.

 

i dont know what burning coolant smells like, i know it looks really white coming out exhaust

 

If white vapor is coming out after a good ten mile run, and it collects on your palm,
good indication coolant.
Pulling the spark plus and looking for the cleanest plug tells the story of the leaky cylinder.