What is the proper fluid to top off Roaster battery cooling?

[Stewie26]

My roaster's battery cooling fluid reservoir is just barely above the minimum mark shown on the side of the reservoir. Can anyone advise the proper fluid I can purchase so I can top off the fluid to the proper level? Any help would be much appreciated. Thank you.

 

[ML Auto]

Propylene glycol antifreeze (Sierra) was used because it is environmentally friendly like the car, but all the components are compatible with regular ethylene glycol antifreeze (which has better cooling and freezing properties). Mix with distilled water, or premixed.

 

[Stewie26]

Propylene glycol antifreeze (Sierra) was used because it is environmentally friendly like the car, but all the components are compatible with regular ethylene glycol antifreeze (which has better cooling and freezing properties). Mix with distilled water, or premixed.

Thank you ML Auto.