Syncros and automatics seem to be particularly effected but increased fuel
consumption during colder weather is normal for a number of reasons. 

Cold weather starts, longer warm up periods simply require more fuel. 
Thicker oils require more energy to move, pump, splash, etc. There is also a
lot of increased drag from the thicker lubricants. 
Colder air is denser! It takes more energy to push a vehicle at speed
through this thicker air. I really see the difference with the motorhomes.
That is also why some see improved fuel economy at high altitudes. 
The colder-denser air also effects engine operation. While this helps an
engine produce more power more energy is used.
This is minor but energy is used to operate lights, heater fans, defrosters,
etc. As alternator load is increased more HP is required to turn it. 
Usage also changes. Trips are shorter, more time is spent idling at
intersections, traffic etc. Whenever the engine is running and the vehicle
is not moving you are getting 0 mpg. 

Dennis

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
MICHAEL H
Sent: Friday, November 30, 2012 11:10 AM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: Gas consumption higher in winter?

Jack - I'm dreading this myself in upstate NY. mileage will decrease with my
Van due to snow tires in the back and lower air pressure all around. better
traction with the same handling is more than convenient - and we DO pay for
convenience - it's empowering to be able to drive circles around newer
vehicles������ =( :D)���� mike

 

________________________________
 From: Rocket J Squirrel <camping.elliott@GMAIL.COM>
To: vanagon@GERRY.VANAGON.COM
Sent: Friday, November 30, 2012 10:37 AM
Subject: Gas consumption higher in winter?
  
I'm exploring this now. It seems that, without any change in driving habits,
my van's mileage is poorer in winter than in summer. I'm talking northern
hemisphere here, and by "winter" I mean "cold" and summer, well, not cold.

I'll be checking this for the next couple months, comparing 10% ethanol gas
v. straight gas.

In the meantime, has anyone else noticed this? Is it common, with a simple
explanation?

--
Jack "Rocket j Squirrel" Elliott
1984 Westfalia, auto trans,
Bend, Ore.