Replacing Coolant

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My radiator is not full to the cap with coolant from my last service 5 months ago, and my reserve tank is empty, so i wanted to just top it up with coolant, however, I'm not sure what coolant my mechanic used last. Can you mix two different coolants?

If I want to replace my coolant my manual says:

Amount of Coolant (when undilutede coolant of 98% concentration is used)

Ambient temp
-10 degr C

Concentration 23%

Radiator (litre)
0.66

Reserve Tank (litre)
0.14

I'm not sure what the last two refer to. I would have thought you just need to know the concentration eg .23L coolant and .77L soft water?

Never done this before so not sure how important this is. Is my engine going to blow up if I don't get it exactly 23% concentration?

Any tips welcome.

posted by  b1__

Please introduce yourself in the appropriate section prior to asking for help.

posted by  vwhobo

It may help if some specifics were given as to what make and model the car is, when was it built. (1997 Nissan Altima for example)

Some manufactutrers have different coolant specs depending on when the car was built. These specs should be listed in the car's owners manual

posted by  tbaxleyjr

To answer the other questions

The antifreeze concentration determines the mixture freezing point
30% antifreeze-70% water - +4 F freeze point
50% antifreeze - 50% water - -34F freeze point
60% antifreeze - 40% water - -62F freeze point

The boiling point of the mixture changes as well.

Most manufacturers don't like running over 60% concentration antifreeze since it makes the mixture thicker and slows the flow rates

Distilled or soft water is used since regular tap water has dissolved minerals which precipitates out in the radiator core

posted by  tbaxleyjr

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