I will do a tune up next week, I will replace the coolant. So what would be the best mix for a 305 TPI that is in Canada? The car won't run from november to april. It will be stored but not in a heated garage. It's very cold around here in these months with lots of snow. But I wan't my car to have the best mix when it get hots again. Thanks!

 

Usually a 50/50 mixture is fine. I live NL, and my car see's the road until October (at least), and then out again in April. It can be pretty cold here during those months, and I have no problems with that mixture.

 

You can use a hydrometer or refractometer to tell you the freezing point of your coolant. I prefer to drain the coolant when the car is stored for any length of time.

 

If I put more water than coolant, will my engine run more cold? If yes, what would be the best mix of the two? Without risking to freeze this winter.

 

Are you planning on driving your car this winter??

 

No, that won't affect the operating temperature much.
But it will raise the freezing point, meaning it will freeze sooner. A 50/50 mix is pretty standard.
Our systems hold about 15-16 litres, so if you drain the coolant and add two full 4 litre jugs of fullstrength antifreeze, then top it off with water (preferably distilled to remove particles that can rust) it will mix up to a bit stronger than 50/50 which should be good to like -45° C.
I've had no problems with that mixture here in New Brunswick, and it can get down to -40° some nights.
A cold chill ran down my back just thinking about it...