Alright, so I've got a 2.2 base model completely stock and 144,xxx miles. I drive it around 50 mile round trip a day probably 3,000 miles ago I sea foamed and changed plugs and oil but right now I'm only getting 25 mpg when I used to be getting mid to high 30's. I know I need a fuel filter and air filter but don't think that would cause this bad a drop. Any suggestions, thank you.

 

Air filter might...

 

Dirty air filter, dirty maf sensor and dirty fuel filter would make your mileage drop, check for cracks on your intake flex section if you are running stock intake.

 

if you live somewhere that it gets cold i know the gas changes and causes you to get worse mileage.

 

Dirty air filter shouldn't really effect mileage on modern cars as the computer adjust the amount of fuel to the amount of incoming air. It would effect performance though. I know on my old 2.2 the fuel filter is located in the gas tank and is pretty much maintenance free.

-How is the pressure in your tires?
-Cold air is more dense so that increases drag a bit as your pushing against a greater concentration of air.
- Winter gas formulation does decrease mileage as well.

But all of those couldn't be contributing to a 10+MPG drop.

 

Yup

 

The fuel filter on my cobalt which is an 08 isn't in the gas tank it's right Infront of it and super easy to change if you've never changed it maybe try that

 

How many other regular maintance to the car have you done? Ex. Spark plugs, fuel filter, and etc.

 

This was the air filter I did change it today and added air to all four tires they were around 23-25 psi so I aired them all to 32 psi, will check mpg results in the next few days.

 

Fuel filter would be a good place to start. With almost 150k, degradated performance is to be expected from normal engine wear. How quickly did the economy drop, and do you keep up on maintenance intervals?

 

Yeah I try to change the oil every 5,000 miles and I ran half a tank through with the aired up tires and filter, averaged almost 28 mpg, should the fuel filter be my next step then?

 

If the fuel filter hasnt been changed in 144k miles, its long overdue anyway. Its one of the cheapest, easiest things to do yourself. You just need a quick dis connect tool and some patience. They can be a pita due to where they are located. Road grime/dirt get in there making it not such an easy dis connect. But without buying diagnostic tools or paying someone to check it out, I would go there next.

 

Okay thanks I will get one this weekend and put it in, I have a scan tool but am not completely familiar with all the readings to check for the mpg loss.

 

Well what readings are you confused with? Does it give lt and st fuel trims? Does it give you o2 sensor readings? ECT temp? MAP or TAC, voltage at what RPM anything to help a brotha out? (ut oh, going to hell for that one huh?)

 

Here is another thought, if you are toe'd out on your alignment that would hurt mpg too,

 

Alright so I haven't messed with the colbalt too much in awhile because I recently purchased a jeep wrangler, but the Balt is now getting 24 mpg and is slow on the street? My tool shows all the listed stats, it does full data sheets I just don't know what numbers would lead me toward a fix. The only maintenance I have yet to do is the fuel filter and believe my alignment may be a little off, will this still account for 10+ mpg loss or should I be looking deeper?

 

welcome to winter where gas is cold, oil is cold, tires never get to operating temp, and the pavement is cold.

How long does it sit warming up in the morning? Running winter tires?

 

I undertand the winter circumstances, but my jeep at most is 4 mpg less in the coldest weather, but at most 2 minute warm up( the gf drives it she isn't patient) and no winter tires

 

Long term above +10, ahort term not cycling somewhere around -5 to+5 could help explain, but not pin point a component. Average 02 above 450mV would explain, but without graphing voltage transitions won't be definitive either. Honestly, I would change the fuel filter, look for vacuum leaks between the maf and throttle position sensors, buy gas at the same place (preferably without ethanol), check tire psi, trans fluid level if auto and see if milage increases with weather temp. Or right after any of those potential changes since you have no DTC's. Soooo many things can affect economy.
Edit: and tell the old lady to wait till at LEAST 180* coolant temp before shutting it off. Preferably 192*