poor mpg
 

i have a 04 ecotec with the origional plugs i think. i bought it off my parents for a dollar and i believe my dad hadnt changed the plugs and i only get 20 mpg in city and 27 highway any suggestions?

unplug the battery overnight,

that willl just reset my coputer right

yepp, i was only gettin 220 street and 300 highway, i reset it and got like maybe 15 better on street

i have to work tonight from 8 to 1am so when i get home i will disconect it

You're only off by 2-3 mpg tops, hows your driving habits, do you drive like an ahoe? Even if you did, you should get at least 30 on the highway, so start with the basics, oil change, air filter, and the spark plugs you mentioned is a possibility too.

i just put a wai on oil change needs to be done and plugs i have 80400 miles on it

It wouldn't hurt to change the plugs but its probably not going to improve the mpg, I would look into other possibilities.

it also overheats at idle

Well then you've obviously got something else going on, you need to get that checked out.

forgot to mention that one

Are your fans working when it heats at idle? Also, when your car is heating up, is your AC on? Mine will also heat up a little at idle if I don't turn the AC on. Also, check for any lights turning on in your dash.

yeah could be the following:

clogged cat
o2 sensor
wires
coils

i know my car needs a whole new exhaust. my last fill up i only got 200 miles out of a tank!

im in the process of changing the dexcool out for the green stuf i have 75/25 water to antifreeze right now. it gets up to 3/4 hot until i start going and it doesnt overheat as bad if the ac is on. i also thought it might be my thermostat

Whatever you guys are talking about makes absolutely no sense whatsoever

yea ur supposed to turn on the heat when your overheating LOL

I dont know, but I think that on my car, when you turn the AC on, it turns the engine cooling fans on as well. Several times its happened to me, that Im at idle with the AC off for a good while, and it starts to heat up. The moment I turn the AC back on though, even if I dont go and am still at idle, in less then a minute, my temperature will go back down to normal.

my car also starts heating up at idle when its warm out... it just goes between half and 3/4... so not to shabby, and my motor is about 6 months old.

and cactus... he isn't getting close for the ecotec. on the highway... i average 35-40mpg, and i only get about 26mpg city... but i drive her hard

Thats unusually high for an ecotec, especially if you drive hard, assuming that your calculations are correct. The epa ratings of 21-24 city, and 30-32 highway, are very close to real world mileage. I got 21-23 city, and 30-35 highway. Over 35 on the highway is an anomaly, and so is more than 23-24 in the city, which in your case is most likely not true city driving. More like rural city driving.

my mom told me when she had it she got 25 city but i also dont drive like her i am into it a lot