In 90% of the places snowmobiles will be used, 50/50 is NOT enough antifreeze. Go 60/40 for protection. We are not even into official "Winter" and my thermometer is reading -25. Where my wife works, their official weather station read -22 in the early evening.
Rider-
I have to tell you that I don't doubt you, but I am skeptical that what puddled the antifreeze under your friends race car was caused by the expansion of ice crystals in a antifreeze solution. Clearly there are lots of other things that could have caused the leak and perhaps the cold simply made this shrinkage the culprit.
Almost (but perhaps not all) antifreeze is "over stated" in what coverage it will protect your engine.
Please take some time to try a simple test which I have done many years ago.
Take a glass jar, miracle whip etc, and fill it with 40% antifreeze and 60% water. Fill it to the very top. Use any jar with a tight fitting lid. Now shake it up and put it in the coldest place you know of.
Look at it from time to time, especially during this cold snap. You will find that tho it can form some ice crystals, there is not enough ice crystal formation to expand the fluid to burst the jar. Glass conducts cold well.
This is like your engine.
Many years ago, folks simply used alcohol and water in the radiators and got by pretty well in those days, tho occassionally the alcohol would evaporate and the mix would not be sufficient and on extremely cold days they would boil over from frozen radiator.
But the truth is that as long as the coolant stays liquid, then it works. But here is the most important part:
The more water you can use and still be protected the BETTER your cooling system will work, because water cools far better than the antifreeze material.
This is why some folks including me, who had overheat issues were "steamed" to find out that somebody at Yamaha doesn't understand that water is required to cool an engine and that using more antifreeze than is needed is worse. Far worse.
Now you can go along with using a poor conductor of heat transfer if you want to and you can go back to the fundimental discussion of thermodynamics that the fellow has kindly put in words for all to understand, but by doing this you are CONSTANTLY causing poor heat transfer and thus needlessly putting your expensive engine in a heat range that cannot do it any good, and likely will be shortening the life of that engine. For some who peddle the sleds early, this is not important and screw the dealer or poor fellow who get your used equipment. And dealers get well paid to fix those engines after they get overheated and shortened lives.
I intend to use only that which is necessary to keep her from freezing up. I don't intend to run her any hotter than I have to, which is why I changed the antifreeze to a 50 / 50 mix, which is all I have run in my car engines for years and years. I have never had a problem with doing that even to static -34 below zero in cars that run 70mph down the freeway causing windchill of -100.
More is not always better, and in fact in this case more is actually worse.
But again you decide. If it makes you feel good, then do it. But it is not sound maint. decision. And if your sled is like mine, with marginal heat transfer engineered into it, then this point is even more important.
I can think of lots of places where more is better, but this ain't one of them.
