Gas Mileage Dropping; what can it be?

[Rizz-rolla]

I've noticed since Sept that my gas mileage has been getting worse. I drive down this big hill every day to work and during the summer when coasting down this hill (w/ foot off gas) I would actually pick up speed. For the last couple of months now coasting down this same hill, i actually start to slow down. Could the cold weather be having that much affect on my lube/bearings? Is something else going on here? I'm experiencing the same thing with my Tundra (although that beast never picked up speed going down hills).

[punter]

Tyre pressure???

[freakinbox]

have you adjusted anything on the car within that time?
I'd say check your tires.

[rezzle]

Tire pressure and cold, weather. Dive around for a half hour or so then try it again you will see the difference.

[KnightX_AE86]

also the longer u warm up the car the more gas it use

[TBayToyotaBoy]

Um, tire pressure shouldn't have THAT much affect on your downhill coasting. Up here in the Frozen North, it gets down to -20 (Celsius) regularly, and it's still not necessary to add air (down to -30 degrees, well that's another story). I've had the same problem in all three of my cars and it's either been: a) slightly or very seized caliper, or b) wheel bearing.

Considering costs, try the "adding air to the tires" approach first and hope for the best...