I'm not sure to what extent the ideal gas laws apply to air in your
tires, but the cold will reduce the pressure in them. This makes it
difficult to inflate them properly. Also at start up the batteries are
cold and electrical acceleration is much lower than normally.
I'm in Alexandria, Virignia and have been getting around 36-42 mpg but
I see it picking up with the warmer weather.
One of the things I find very noticeable now is whether a trip is net
uphill or downhill. When I come in to work it is clearly net downhill
and I get stretches of 80+ mpg coasting down the hill on I-395 at 50-60
mph. I pay for it somewhat on the way back home but usually the car is
warmer because it spends the day in underground parking.
I have put STP Fuel Treatment in it once, but afterwards got worried it
would not do the fuel bladder any good. Does anyone have informed
comments on Fuel Injector Cleaner and the fuel bladder?
D'ohh!! Yes, tire pressure makes a noticeable difference. It should be
checked monthly, or whenever the average daily temperature changes much
more than 10'F.