Dominique:
  For the most part, methanol in the fuel system is bad.  However,
sitting on the side of the road slowly freezing is also bad.
Unfortunately, many times, fuel gelling is blamed for a simple case of
frozen water that sits at the bottom of the tank, frezes, and restricts
fuel flow.  What has been done for years around here is when this
occurs, add alcohol, it goes primarily to the water, thaws it, end of
problem.  Diesel fuel simply does not gel as much as people think.
  How to tell?  Same conditions as when your gas car freezes up.
Unseasonably warm day, followed by a cold snap. What happens is the warm
day melts all the water that has been hanging around in the tank as
frost deposited by condensation.  This pools, then when it gets cold
solidifies in either the fuel line or tank.
  I carry kerosene, and alcohol in the trunk of the Jetta.  I've had
both things happen- ice and gelling.
  Kind of similar to Loren adding gas to prevent gelling. If it's done
with a measure of sense (kind of like most things), it works just like
intended.  Wouldn't want to dump in a huge jug, but just enough to melt
the ice.

  When they refer to no alcohol, I know, I've read that too, and just
chalked it up to the ad people sleeping through chemistry classes.
"Alcohol.... that's what you drink, right?  Nope none of that in here."
Also public perception- ads have been telling us how bad alcohol is in
diesel systems, but at what concentration?  Too much, sure, but at low
levels it just doesn't matter.
-James