It sounds like you have a mis-conception or two about synthetic oils -- and if you're not familiar with Amsoil, it is likely due to the fact that you've tried other oils called "synthetic" that perhaps were not.
Mobil 1 (in certain formulations!), Royal Purple, Redline, Amsoil, and a couple of other lesser-known brands (Mystic, etc.) are actually true synthetics. The balance are regular oils with synthetic additives, which are now able to be sold over the counter as actual synthetic oils.
Of these, Amsoil is (IMO) the industry leader, and still king. They were the first, and their oil is a long-chain-molecule blend that will protect to very high temps and loads as well as flow freely at very low temps -- so freely that it is like fall weather in deep winter. Though I've not lived where it gets to -60, I did live most of my life in Central Wisconsin, where we saw -25 fairly regularly, so I'm aware of what happens once the thermometer heads for that cozy little bulb on the bottom...
What might have caused any "problems" you saw in a motor is the fact that the synthetic oils tend to have a higher detergent load, plus the fact that they find their way into EVERY crack and cranny possible -- great for best lubrication, not so good in an old motor with worn seals...
Amsoil will not cause more wear -- period. In fact, it will virtually halt oil-related wear because it is SO high in lubricity. I don't recommend using it in a new or almost new vehicle because it will never break in properly!
Another worry that I've heard over and over is that "once you run synthetic oil, you cannot go back to regular oil." That is total BS. No such thing. It would be stupid to go back, as you loose all the protective qualities of the synthetic oil, but otherwise, no harm is done. They are perfectly compatible.
This is what I run in my own trucks:
http://www.amsoil.com/storefront/svg.aspx
Notice in the spec chart at the bottom of the site that it still free flows at -60F. I dare you to try that with any other gear oil! They turn to peanut butter at around +15F.
I'd run it in a heartbeat if I lived where you live.
There are two ways you can get the stuff (and note: I'm NOT a dealer -- just a VERY satisfied customer!). Either buy it online from some dealer that sells that way, or become your own dealer. The buy in for a dealership is cheap -- around my area $10 a year to get dealer pricing, with NO inventory required. You get that back on the first oil change!
Finally, there is no oil that lasts "the life of the vehicle." That is another joke. Amsoil is an extended change interval oil, but even it doesn't claim "life of the vehicle" use. What the manufacturer is saying by "life of the vehicle" is that if you leave the oil in your truck and never change it, you will be purchasing a new vehicle about every 75,000 miles, right on schedule -- which is their idea of "life." Their idea is definitely not mine. I tend to run 200-300K on my stuff, and then I either sell it in good condition and still running or part it out if the body is gone. Either way, with the synthetics, the running gear is still running great at 200+ thousand miles.
