Tap water will do IF IT IS NOT well water. Water from a river has far less minerals and salts in it than well water.
But in your case, chances are you are closer to a store than a river. So buy some drinking water in bottles and use that.
So 50/50 is close enough. Next time it is low you add antifreeze to keep the mixture happening (for obviously you got a leak.) Antifreeze keeps the waterpump seal lubricated and keeps the boiling point higher than 212 degrees F
Yes you can add water anytime . Make sure you check before long journeys
yes, but it is good to try and keep a 50/50 mixture.
If you add pure (undiluted) antifreeze, you generally want a 50/50 ratio between antifreeze and distilled water in your coolant system. (Do NOT use tap water - the minerals in tap water can mess up a coolant system.) If you've only been adding pure antifreeze, which is what it sounds like from your question, you need to balance out the pure antifreeze with distilled water.
In the future, if you want to skip having to mix pure antifreeze with water, you should be able to find diluted antifreeze in any car parts store or discount store where it is premixed in the package. Just look for 50/50 Prestone, etc. What sucks about that is that you're basically paying for a half-water mixture, but it is convenient to have on hand if you're not a gearhead.
What light?
Can't tell what you mean?
If you mean there is a light just for coolant level, then of course you need to fill more.
If you have only water, then that is better than nothing.
Next time, just add pure antifreeze to restore the right 50/50 ratio.
But very few cars have a coolant level light.
More likely they have alternator and oil lights.
Some have a temperature light that would likely be more like loose water pump belt, bad thermostat, head gasket, etc.
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There is two ways to buy antifreeze. You can buy it already mixed 50% antifreeze and 50% water, or you can buy straight antifreeze which you should mix with water. Don't use straight antifreeze in your car, if it is straight antifreeze there should be an chart on the container that tells what mixture to use to obtain what freeze point. You need to read the container to see what you have.
