alright i guess im going to add the one millionth thread to this category. had the car for a little over a year... first six months great, 28-32 mpg. needed new tires so i put them on. do regular oil changes. saw gas mileage go down, last week, calculated, 16mpg! took it to the garage (where i bought) he said oil was over filled about a quart and I had 2 bad front ball bearings... I dont see how this would cut my mpg in half. worst part is its 90% highway as i work an hour away... its an 07 cobalt. fuel filter, goign to take it to advanced auto to check for codes after work tomorrow... anybody have any help tips know whats wrong... i'm spending over 100 a week in gas, killing me.