Antifreeze: brands and underlying theory

[stone36]

Thanks rangema,

I am also wondering what brand of fluid I should use with the water, and if it is OK to mix with what is currently in there (assuming that it is original volvo fluid).

Thanks

[BEJinFbk]

70/30 is a suggested ratio for winter when it's cold becasue the 70% antifreeze helps prevent the water from freezing. .

70/30? Really? No one here does that...
I've never mixed anything other than 50/50.
-60? No problem.

[jblackburn]

Can any "HOAT" premixed 50/50 work? Volvo also has the warning on the reservoir about not mixing different types of Anti Freeze as well.

Yes. It just means don't mix Dex-cool (orange) or other colors of antifreeze together. See if you can get your hands on some of the Zerex G-05 or other HOAT coolant.

[FlyingVolvo]

These systems take less than two gallons, so personally I don't go cheap on it... I just buy the 1 gallon of distilled water and have peace of mind.

[JaneDoeS40]

I realize this thread is a little older, but I have recently bought an S40 1.9T and I have a concern regarding the coolant. Having had a car overheat on me before I want to be absolutely sure I get this right (it's been over 6 months and I'm still traumatized). I have found that Pentosin is a Volvo recommended coolant for my car, but I have no idea what the previous owner has used and I'm worried that if I just pour some Pentofrost NF into the reservoir I'm going to ruin my car. I'm kind of getting the idea that, as long as the coolant is the same color (green with green, orange with orange) then it's okaaay to mix different brands...am I way off here? And if that's a bad idea, what would you suggest (I've already tried to contact the previous owner and have thus far received no response)?

[jimmy57]

Many of the coolants are not compatible with each other. Even the coolants labelled as compatible with anything may not actually do anything harmful but they may take the coolants life from 5 years to 2 years.
Since you have doubts drain it and flush first with tap water. Then get 8 gallons of distilled water. It is a dollar usually at dollar stores and even less at Wal-Mart. Flush it with 6 1/2 gallons of that. Now use the Pentosin and distilled at 50/50 mix. Maybe a little exra antifreeze to compensate for some of the flush distilled that is left behind.

[E Showell]

Guys -- I'm not a scientist here, but there is a reason not to run straight water. As I understand it, and I'm reaching back to college rocks for jocks here, the reason you add anything to the water you run in your cooling system is to take advantage of the properties of solutions. When you dissolve anything in water (and I'm counting mixing antifreeze in here) you get both a boiling point elevation AND freezing point depression. Thus, a mixture of antifreeze/coolant and water will boil at a higher temperature in summer -- thus delaying the point of boilover -- and that same mixture will also freeze at a lower point in winter thus giving your engine block freeze protection down to lower temperatures than will straight water.

The various charts on the sides of antifreeze containers show that altering the mix ratio increases or decreases the amount of freeze protection -- up to a point.

You are searching for an eutectic mixture -- the eutectic point being the ratio of components that gives the lowest possible freeze protection. There is a synergystic effect here. That is why you don't get any additional protection from running straight antifreeze in winter. You could choose to, I guess, but I don't believe you would achieve superior freeze protection than could be obtained from an eutectic mixture of antifreeze and water.

The eutectic concept is why salt gets spread on roads to melt ice (it depresses the freezing point to below 32F and hopefully keeps ice from forming on the road until well below 32F) and why rock salt is added to water to make ice-cream -- to depress the freezing point and chill the cream below what plain icewater would give.

Physical science lesson over.

[MilehighV70XC]

I run 50-50 or No more then 70-30 water to antifreeze. Some people run the 70-30 to help prevent the aluminium in the cooling system from corroding. I run 70-30 in my summer car and 50-50 in my Volvo daily driver. Another big reason not to just run water I didn't see mentioned in this thread, the antifreeze acts as a lubricant for the water pump and prevent premature failure.

[jimmy57]

When you go to higher concentrations you increase silicate drop out.
The silicates in the coolant are in a higher concentration and the precipitation rate will be higher on the edge of cores of radiator and on surface in engine.
Once you pass 50% coolant the gains of additional coolant for anything but freeze point depression rapidly diminish. Even freeze point depression diminishes on a degree depression per % increase in coolant.
Car manufacturers list 50/50 with recommendation for increased percentage only when needed for Arctic climates.
100% water is to be used for flushing only. Distilled is best as its lack of other chemicals makes it dissolve some precipitates readily so they can drain out. Some flush agents have some risk to water pump seal so if there is no reason to think it really needs flushing with a cleaner then don't use it.

[JDS60R]

When you go to higher concentrations you increase silicate drop out.
The silicates in the coolant are in a higher concentration and the precipitation rate will be higher on the edge of cores of radiator and on surface in engine.
Once you pass 50% coolant the gains of additional coolant for anything but freeze point depression rapidly diminish. Even freeze point depression diminishes on a degree depression per % increase in coolant.
Car manufacturers list 50/50 with recommendation for increased percentage only when needed for Arctic climates.
100% water is to be used for flushing only. Distilled is best as its lack of other chemicals makes it dissolve some precipitates readily so they can drain out. Some flush agents have some risk to water pump seal so if there is no reason to think it really needs flushing with a cleaner then don't use it.

+1