Something always to remember on mixing coolant and water:

The more anti freeze you have in your system (like 70% coolant, 30% water for example), the more likely you will have a leak. Anti freeze finds leaks before water. So test your mixture and adjust to your climate accordingly.

 

One more question: Is it normal for my coolant to be bubbling in the expansion tank?

 

Let me clarify, it only seems to bubble while the car is running and only where the coolant is returning, at the small hose at the top of the expansion tank.

 

Only run your coolant at a 50/50 mix for the maximum effect.

 

Mine doesn't bubble (once all of the air is bled) unless it is overheating.

 

25water/75coolant is to "cover their butt". Water has far superior heat-transfer capabilities than anti-freeze. Straight water will get you the best results, but we all know what an early frost would do to our already fragile engines.


50/50 is the best rule-of-thumb (and what I do), but even that is overkill with a built in safety factor.


IF you want the best cooling abilities, you need the SG chart for your coolant (as mentioned) and then measure the mix. The chart will tell you at what temperature you are protected too.


But remember, if you skirt the edge (maximum efficiency) you MUST keep routinely check your coolant, because its efficiency drops over time. And you can risk freezing your engine.


Hence 50/50, fill and forget. With our Disco's tending to run hot, I wouldn't go 25/75 (unless you meant 75 water, 25 coolant).

 

Mike, really?
Anyone who's ever read an antifreeze label knows that isn't true.



I run 50/50 but only because it's appropriate for where I live and is easiest to mix.
When I lived in the north I ran 60/40 or 70/30 coolant/water.