Is it really a big deal if I use tap water in my coolant instead of distilled water? What is the difference anyway?
All right, is there a winter and a summer coolant? Actually, no. The coolant in the car, and it is called coolant now not anti-freeze, is year round. You use the same thing all year long. If you should have a leak, well in this time of the year, you could add a little bit of water to top it off in an emergency, as long as you get the leak repaired and get the proper concentration- 50% coolant, 50% distilled water- back in the car as soon as you possibly can.
The question comes up: Do I use regular tap water when mixing my coolant and water together? No, you should use distilled water or better yet, de-ionized water. The reason for this is that tap water has minerals that can deform deposits inside the radiator and the cooling system passages of your engine. And over a long period of time they can lead to over-heating.