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Larry, I respect your remarks and will offer some justification of mine.
"I respectfully disagree with the recommendation of the 25/75 coolant/water mix. Coolant (a/k/a anti-freeze) not only lowers the freezing temperature of the water but also raises its boiling point. Therefore, a 25/75 mix is going to boil over sooner than a 50/50 mix."
Correct. The standard 50/50 mixture will freeze at (all temps approximate) -37F and boil at 256F with a 15lb pressure cap. The standard Saab cap is 7lb so the boiling point of that mixture will be lower if you use the standard cap. The freezing point will not change.
A 25/75 (coolant/water) mix will freeze at about +10F. I may have misstated this previously as -10F, sorry for the mistake. I do not know its boiling point with either 7lb or 15lb cap, but it will be higher than 212F and higher with the 15lb cap than the 7lb cap.
In many regions, including mine, the coldest winter temps do not approach +10F so 25% coolant is more than adequate for freeze protection. If this seems marginal, a 33/67 mix is good to 0F and may satisfy. In extreme climates, a 67/33 mix (very heavy on coolant) will freeze at about -60F. This is known as a eutectic mixture which has the lowest freezing point of a coolant/water mix. At higher coolant concentrations the freezing point rises, and pure coolant 100/0 freezes at about -6F.
I am not readily finding a chart for boiling points and they vary considerably with system pressure determined by the pressure cap. Boiling point with a 15# cap and 50/50 mix is 256F. Boiling point with no cap and 0/100 mix (pure water) is 212F (at sea level). Boiling point will be higher with increasing coolant concentration and also higher with increasing value of the pressure cap, so let's agree that with 25/75 coolant/water and a stock 7# cap it might be around 230F.
I believe that the V4 temp gauge is centered at 180F and approaches the red at about 220F. If so, the gauge will warn you (if you're watching haha) well before the danger zone, even with plain water and no pressure cap.
In normal circumstances as designed (Sweden, right?), no problem. We in hot climes need extra help. There are many ways to get that extra help, I have posted before re oil coolers, & others re radiator improvements.
One of the ways to get extra help without spending money is improve internal heat transfer within the engine/cooling system.
Antifreeze inhibits heat transfer. The more coolant in the system, the less efficient the transfer of heat from engine block and head to the liquid coolant, and likewise from the liquid coolant to the radiator which pulls heat out of the system to the atmosphere. A pure water system cools better than one with antifreeze in any concentration. The less coolant, the better the heat transfer.
Accordingly, if you need to maximize heat transfer out of the engine to the atmosphere, you need to minimize coolant concentration.
Racers generally use water only or add Redline Water Wetter, for two reasons. One, their engines run cooler; Two, antifreeze on the track from a busted hose or whatever is hazardous to fellow racers.
Ethylene glycol is the active ingredient of most antifreeze. It is thicker than water. It is not green, the green is dye. It does not pump as well and does not transfer heat as well as plain water.
Conventional antifreeze formulations have ethylene glycol as the main ingredient but have a number of additives to improve performance of the system. These include anti-foaming, anti-corrosion, lubrication, probably a batch of other stuff.
These additives are optimized for a 50/50 mix as generally recommended. The general recommendation is to change coolant every 2 years. I suggest that if one runs a 25/75 mix, with a flush/exchange every year, the additive level of the mix will be adequate for that period.
The most important thing in our cooling systems is to keep them in top notch shape with regular changes/flushings and to use a premium coolant. The cheap stuff works but you will end up paying more in the long run when you need to have that radiator done.
Yup. What is a "premium coolant"?
posted by 198.69.25...
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