Gas mileage in the winter.

I have a 2000 Tiburon. I've noticed in the past that gas mileage in my car usually goes down in the winter time. Over the summer, my car was getting 280 to 300 miles on a full tank of gas but in the last couple weeks, it's been cold and rainy and now I'm only getting around 240 or 250 for a full tank of gas and it's not really winter time yet. Should this concern me? Besides the gas milage, my car seems to be driving extremely well and the engine is running smooth and quiet. It was suggested by a friend from work that the problem I'm experiencing is probably due to the cold air intake I installed in my car. He seems to think that because my car is pulling in nothing but very cold air, it's causing my car to close up the engine vents thus resulting in lower gas mileage in my car. I've already ordered a short ram intake as I figured it is a good idea considering how wet it gets this time of year and I'm hoping that will solve part of the problem.

So my question is if this is normal for my car and should I be worried? And does anyone here have any advice on how to solve the problem?

sorry, but your friend dont know shit.

cold air is great for an engine. its packed full of more oxygen molecules. your gas mileage has gone down because you are sucking in more oxygen molecules. your ecu sees this and adds more fuel to the engine so you dont run lean and destroy your engine.

240 on a full tank is low though. you either have an automatic, rev up everywhere, or need to do some routine maintenance to get it back up.

what you should really give when you have problems like this is your mpg too. you really dont know if you used a full tank or not, and that causes innaccuracy.

Winter fuel contains ethanol to reduce emssions. That might effect MPG.

Winter fuel contains ethanol to reduce emssions. That might effect MPG.

it will also reduce the freezeing point