Engine coolant has three jobs.  The first is to protect the aluminum engine parts; the second is to keep the engine from over heating and the third is to keep the engine from freezing.

When a shop checks your coolant they put a test strip in it to check the acidity of it.  As the coolant deteriorates it becomes acidic and starts to eat away at the aluminum engine parts.  The shops also have another tool to check the temperature of the coolant.  When it is new it should go down to approximately minus 50 degrees celcius.  A shop will usually suggest doing a coolant flush when the coolant doesn’t go below 30 degrees Celsius.  What some shops have told me is that when people are buying cars in the Southern United States the coolant in those vehicles doesn’t have the cold weather package in it, so the coolant will need to be changed when it comes to Canada.

If your car has overheated and you lost your coolant,  in a pinch you could add water to the engine to get you through, but before you do anything make sure it has cooled down.  Also, this isn’t something you would want to do on a consistent basis as water doesn’t have any lubricants in it to help with the water pump.

My boyfriend drives a big Ford F450 and his heating system in the vehicle wasn’t working properly. He took it into the shop and they didn’t really have time to deal with it so he was driving it.  One day he looked at his temperature gauge and the engine was over-heating.  I just happened to be following him in my car so he pulled over and I had to drive him to the gas station so he could buy a jerry can and fill it with water.  It took almost the whole can of water to fill it back up. Putting water in will work in a pinch to get you back on the road.  The next day he took his truck in and they ended up putting a new radiator in it as it was leaking!