No, NEVER use tap water! Just pick up some pure distilled water from the grocery store. Use only distilled, nothing else. For antifreeze, use an ethyline glycol base coolant like Prestone (green or orange). Mix both up into a 50/50 mixture. -Robert vin 6585 --- In dmcnews@xxxx, "K Creason" <dmc4687@xxxx> wrote: > My overflow bottle is low (dry!). > I obviously MUST add something immediately. Can it just be tap water? Soft > tap water or hard water? Distilled? > Do I need to add special chemicals because of the aluminum engine like the > Northstar engine requires? (so I hear)... <SNIP>