Poor Milage in Cold Temps

[capy]

I have a 1991 Explorer Sport, (4L) that appears to be getting poorer milage in the winter (14mpg) compared to the summer (17mpg).

I have been keeping a nearly continous record of my gas milage since January 2000. I was living in Phoenix AZ in 1991 and my milage stayed around 17mpg witnter or summer. I moved to Ontario Canada in the summer of 2001 and have noticed I now get poorer milage in the winter but about the same as Phoenix in the summer. I did change the thermostat in the end of 2001, because it was not closing and thus taking a long time to heat up, but this did not change my milage.

Is this cold temp/poor milage an indication that I am having a problem with a paticular component such as, a O2 sensor, fuel pressure regulator or MAF sensor?

 

[Alec]

Usually there are 2 main reasons for worse mileage in winter:
1) gasoline is less pure to help with emissions, but it doesn't burn as efficiently (more oxygenated)
2) air is denser due to colder temps and with more air comes more fuel used. This is also why it may seem like you have more power in colder temps.

 

[capy]

Thanks for the response. I guess its nothing to get to woried about as the milage seems in line with what most people are reporting on this web site.