Bongo Fury

in December last year, I had a friend in England post me an antifreeze tester. I'm not that confident in the accuracy of these things, but it has 2 scales...one above the other. The upper scale registers methanol based antifreezes, and the lower registers glycol based antifreezes. My antifreeze mix registered "safe to minus 40" on the lower glycol scale, in fact, it floated with almost all of the scale out of the fluid. Now, my query is that even with a 50/50 mix, I would have thought that no antifreeze would protect that far. I also notice that at the local Shell garage, they had (last December) special antifreeze on sale which claimed to protect to minus 40. Apparently the winters here have not been severe for the last 3 years or so, but it often gets to minus 25, or so the neighbours say, and you can get 1 metre of snow in a day. Do I stick with my current antifreeze, or do I change it for the minus 40 Shell "special", and if I do, would it be safe to leave it in all year.
Opinions would be much appreciated.
Cheers
Helen

When I had mine flushed and renewed before last winter I asked for it to be safe to minus 30, as I on ski trips I leave it parked for a week, in resorts where I have previously recorded down to -22. They just used a 50:50 mix of normal stuff and were adamant it would be fine. As it happened it didn't go below -15 on any trip last winter.

Thanks for that, Robin. I am not too sure what mix of antifreeze mine is, but as I say, the hydrometer floats nearly all the way out of the fluid, so it must be a pretty stiff mix. I expect that, as you say, a normal antifreeze is quite O.K. and that the Shell stuff is unneccesary. Personally, I have always believed that for lower temperatures all that is required is a higher concentration of antifreeze. I was just curious about what others may feel about special antifreezes like the Shell offering.
Cheers
Helen