Coolant Question

I kind of have a dumb question. Can I add straight water to my coolant reservoir? I was told I could, but not to do it all the time. I've also been told flat out no. It's a 2006 kenworth T600 if it's any help. Thanks for your time.

 

I guess it depends on whether you have premixed coolent if you must then add demineralized water, but in doing so you will delete chemicals added in coolent to protect cylinder liners and then should monitor with test strips

 

I’ve been adding only water for 2 years.

 

It's got an EGR, no def.

 

I also forgot, yes it does have premixed coolant. (Green)

 

What kind of truck you got? Motor, year, etc? Haha

 

2015 kw t680 Cummins It’s only needed topping off from time to time.

 

Mines a cummins isx aswell.

 

My coolant still looks red so I figure it’s ok.

 

Haha mine happens to be green.