Lost antifreeze during winter storage

[gbest]

I de-winterized my 03 GTXSC today, and noticed the coolant level in the cooling system overflow bottle was right at the bottom.
When I winterized it, it was at least 1/2 way up.
It started right up, and stopped smoking once the fogging oil burnt off,
and ran fine on the hose.

Where did it go?
What should I top it off with?

[DarthAWM]

Hmmmm more missing anti-freeze, I think the underpants gnomes have expanded operations into engine fluids.

I would top of with the Preston 50/50 ready mix.