horrible MPG Options

[xs94st]

hey guys..jus want to know what could cause horrible mile per gallon averages. i've been slowing down n driving 65-70 n still my gas just seems like it just drips out as i'm driving along. i filled up n i'm at about 1/4-1/2 a tank and i've only gotten about 140 miles. im gettin an average of 240-260 miles per fill up. yea.

i have a CEL because i have yet to install my 2nd O2 sensor (i have everything, but i just dont have time rite now to work on 'er)

i changed my oil early and wont need to be changed until the end of december.

i purchase 89 octane gas when i fill up.

new tires in front with 50-60% tread on the rears

i don't use any fuel additives, just the GUMOUT injector/fuel system cleaner when i change my oil.

original spark plug wires, NGK plugs

i use 10w30 royal purp synthetic oil

K&N oil filter


what tests can i run to check for vacuum leaks n such? would those cause bad MPG? anything else that could be checked?

i've read most of the MPG threads n they weren't much help because the stuff i wanted to ask were not there and were not specific to my car, so please avoid recircling me back there. i'd rather have someone help me out in regards to what i have written and requested, not anyone else.

thanks guys

-x

[azian_advanced]

have you tried resetting your ecu? there's a how-to on the main page on how to do this.

[Batman722]

it's because of the 02 sensor. Replace the primary and fit the second, and when you say "original spark plug wires" are they original to the car ? if so, replace them and the cap and rotor.

[94celigts]

Is it much worse then what you usually get. My gas seems to be eaten faster in the winter but i believe because im running heat and the fan constantly, as well more work for the cold engine maybe running a little rich?

[GriffGirl]

Definitely replace the wires, cap & rotor, that'll make a huge difference. Also make sure your air filter is clean, that will also make a huge difference.

[Sinyk]

My gummed up EGR has been causing my mileage to drop. That and cold weather.

[xs94st]

alright thanks guys i appreciate it. and by original spark wires i meant the ones that came with the car. the rotor n cap are pretty new (replaced em when he sold me the car) but he may have effed em up. i'll check my egr and i will hopefully put my o2 sensor in this weekend. i've reset my ecu, so i dont think that is attributing to my mpg problems. thanks all!

-x