whats the difference?

 

if your car isn't at full operating temp. your gas mileage goes to shit.

let your car warm up to 3 bars before you start driving.

 

I averaged about 260 per tank and my CAI improved it to 270... mostly crowded highway commute, about the same every day. Biggest effect I see are ambient temperatures. Both AC and heater cost mileage and, as S2kfrog said, tire pressure.

The December weather may have dropped your tire pressure and if you're using the heater some of your fuel is used to keep your engine at operating temp (as controlled by your thermostat). Another possibility is that the temp range of your thermostat is too low for the winter months, which you wouldn't notice in hot weather.

 

i don't understand the point of discussing miles per tank.

how does anyone know how many gallons they've used per tank? if you use the "light" as a gauge of "per tank" well, that's an incorrect gauge as it is inconsistent.

also, i can get "per tank" anywhere from 210 to 300 miles depending on my driving habits.

I did reach 300 miles one time when I deliberately drove slow as a snail, just to see if I can reach 300.

also, i got 80 miles per tank when i went to the race track...

it comes down to driving habits, and you can't possibly say that driving style is a constant variable because it is not. even though you take the same route to work, you always run into a different number of red lights, pedestrians, slow traffic, smooth traffic, different temperatures etc.

 

with all my current mod below. i get 240-260 which is normal for me.

 

the way i can tell how much gas i use is by how much gas i have to put in when i go get gas. also, every time i do go get gas, i resest the odometer.

 

The OP still hasn't told us where he lives. It may be as simple as "It's cold out now" and/or "you made the change to winter fuel."

 

what is winter fuel? what is the difference b/t winter fuel and summer fuel? why is there a difference?

 

my fill up is about 10-11gallons.. get about 220-240 per tank.. mostly city driving with may be 20% freeway at most.. so i say it's pretty good..

 

Check your spark plug gap. I was getting lower than usual fuel economy. Drove about 75% on a tank highway @ 70 mph and the rest city with hardly any hard acceleration and only got 22 MPG. Replaced the plugs today (105K miles since last replacement per manual) and the gap was at .070, nearly double what it should be per manual specs. I can imagine that would cause some pretty inefficient air/fuel burn.

Car feels like it picked up 15-20 rwhp and is a lot more responsive. I bet I get 260 miles this next full tank. I'm also going to start changing plugs every year regardless of miles.