Bad gas mileage?

OK so lately it seems like my car has been getting HORRIBLE gas milage. Besides that, sometimes when I drive I hear a little squeek kinda sound coming from no where in particular (though it seems to be coming from somewhere in front of the drivers side) and I can feel the slightest change of pressure under my foot when it happens while im accelarating. And to top it off, whenever I take the gas cap off to fill 'er up, it sounds like screwing the top off of a coke bottle, like there's air escaping from it or something. Does anyone know what some/any of this means, and if any of it is related?

how horrible is horrible? lol. less than 15 u think? Does it accelerate/rev smoothly? any smoke out of the exhaust? Do you smell gas at all when you get out of the car?

the gas cap thing though...i think mine does the same thing. i just figured it was a pressurized system.

yea our cars dont get great mileage either way but if ur getting less than around 15 thats pretty bad...i had a problem with my car "stuttering" after shifting gears and i did a reg tune-up, spark plugs, wires, synth oil, and a fuel filter fixed my stuttering problem i havent checked my mileage yet but im sure its a little better...

im not sure if its under 15 i havent counted yet, but It's definitely not nearly what it was last week. I haven't noticed any smoke and it accelerates smoothly, (possibly even faster than usual?) It does do this thing where every now and then when I'm accelarating hard the RPM's will shoot up about 1000-1500 higher than they should, then fall back down and continue raising regularly. What's strange to me though is that even when that happens, I could swear i'm gettin exactly as much power as I would if it was just normal. Does that ring any bells?

Might just be your driving habits. Check your tire pressure, swap your fuel filter if it has 40k on it, toss in new plugs, and see if it gets better.