Dex cool? Or regular anti-freeze
 

Just bought a 1997 Silverado, 5.7 motor. The owner's manual calls for Dex-Cool, but what is in the radiator is the old green stuff. Don't know how long it has been there. Truck runs fine, temperature gauge is fine.
Any suggestions? Thanks.

The Dex is for the motors that came with aluminum heads. Green is for cast iron. Not sure if urs has aluminum.

Thanks

Welcome.

if you do not know how long its been in truck I would flush coolant system.
then install the yellow coolant that mixes with either color.

then you would be good to go.

Yes I agree.

I would go with what the owners manual calls for, and only use distilled water when making the 50/50 mix.

That way you keep the minerals in city water out of your truck.

jvp