Alright to use 5-6 old coolant?
 

I have some left over 5-6 year old coolant. It was opened up but the cap was on for all these years. If moisture did come in it would only be water, which coolant already has right?

Hmmm, I would dispose of it and buy a new bottle. Most coolant these days is ready to pour 50/50. I don't like to use automotive fluids whose seal has been broken and sitting around for a long time..