[quote=AKSARBased on my own experience, I have a very hard time believing 60% in 6 months, for either down or synthetic.
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Yes, it is very unlikely to be the difference between life and death. In most conditions, assuming you have reasonably adequate clothing, you should be able to survive a night inside a car (dry and protected from the wind) even without a sleeping bag. I'm not saying you will be comfortable or happy, or sleep much, but you will survive the night. [/quote]

AKSAR,

The quote you responded to specified DOWN. One of the advantages of a synthetic bag is that they tend to loose less - some of them almost none at all (see Wiggy's bags) partly because they can't be compressed so much. Believe it or not, that is data from testing. Not all the testing has shown the same amount of loss, but all I have seen indicate more than 50%. That COULD be enough to make it life threatning.

A typical set of thickness vs temp is given below.

Effective Temp Army Western Mountaineering
+40F 1.5" 1.5" (3" total)
+20F 2.0" 2.5"(5" total)
0F 2.5" 3.5" (7" total)
-20F 3.0" 4.25" (8.5" total)
-40F 3.5" 5" (10" total)
-50F 4.0"

If you were to have a bag that was designed for -20 weather (using the Western Mountaineering number) and reduced it by 60% you would only have 1.7 inches of insulation. From similar charts that would be enough to keep you warm while doing light work - not possible in a bag inside a car. That could be critical. It would be especially bad if the weather were colder than you anticipated.

Although it is unlikely to be the difference, in most conditions, the idea of equipping to survive is not for the likely circumstance under most conditions. All about the unlikely and the worst conditions.

Even though I love a good down bag, most of the time I use a synthetic one. Particularly where weight and pack size are less important.

Respectfully,

Jerry

p.s. I apologise for the table, I haven't found how to get it to post properly. jf