Danielj........as I just took delivery of my car I have not had a chance to check the mileage......BUT....in driving it home from DC I traveled 122 miles and used a little less than l/2 tank through 1-1/2" of snow/slush at speeds of 32-48 MPH....and I thought my mileage was bad until I read many of the stores above.

 

Check out this site, it lists a number of reasons MPG goes down in the winter

http://www.metrompg.com/posts/winter-mpg.htm

" Have a gander at these calculations for a Honda Civic hybrid at 60 MPH in varying ambient temperatures:

MPH-----AMBIENT-TEMP-----MPG (US)

60------------95----------52.98
60------------85----------52.62
60------------75----------51.16
60------------65----------49.12
60------------55----------47.22
60------------45----------44.67
60------------35----------43.05
60------------25----------41.54
60------------15----------39.41
60------------05----------38.09

Look at the extremes: the coldest MPG is 28% lower than the warmest. (Source.)"

In addition, at colder ambient temperatures if you have a CAI or a turbo system the relative density of air will impact the mass of air that enters the engine based on a given volume (I'm not sure if a standard intake system will be effected as directly). If you don't wanna do the math yourself just follow this link:

http://www.denysschen.com/catalogue/density.asp

At colder temperatures you will be getting more air (similar to operating at a small amount of boost). This increase in oxygen will be sensed by the oxygen sensor, and the fuel to the engine will be increased to maintain the proper air to fuel ratio. Therefore, your engine will actually be producing more HP, however you may not feel this due to the increased rolling resistance at lower temperatures. Before the engine and drive train heat up there will also be greater internal friction resulting in less efficient power delivery.

 

were any of you guys whom were having issues with gas mileage able to fix it? im getting an awful 11mpg on my 04 g35 coupe with careful driving.

things ive done:

always put 93 gas
new air filter
new platinum tip spark plugs
fuel injector/throttle system cleanse
computer analyzer shows sensors working ok

im at my wits end =/

2 codes ive gotten:

p0172
p0442