hey everyone, im hoping someone can help me figure out why im getting such poor fuel economy.

i drive a 2007 Cobalt SS/NA (the 2.4L) with an auto trans. car has 56,578 miles on it and normally gets anywhere between 24~28 MPG. lately ive been getting terrible fuel economy, i fill up on Monday with Sunoco super 93 octane, reset my MPG trip and set off to home. i got nearly 30MPGs on the way! awesome no complaints. well all week i noticed that number slowly dropping. its Friday, ive done about 70 miles since i filled up and my reading is 16.9 MPG! what gives!?! is it just the winter gas, bad O2 sensor or something completely different?

feedback would be great! maybe one of you guys have had a similar problem.

https://mail-attachment.googleuserco...q4hp7YXAq78-Zc

^ as of today

https://mail-attachment.googleuserco...cN6To&sadssc=1

^as of monday

 

Do you have any check engine lights on?

 

maybe you are driving it like a v8 ?

 

no the Check engine light is not on and neither are any other lights

hahah no i dont, i baby my car lol

 

Verify to make sure that number is accurate by actually filling the tank and seeing how many gallons it takes?

 

Yeah you cant go by the mpg on the cluster

 

winter gas

 

the number seems pretty accurate, i have a little more then a half a tank, ive done about 70 miles since ive filled up. ill have to write the numbers and and do the math the next time i fill up

 

Because RACRCAS?

 

 

Thats right, i forgot that the cobalt's a race car! hahahahah

 

16.9 isnt winter gas. Theres a problem.

 

evap leak, had a 2.2 06 go from 42mpg to 5mpg in a day, found a very small leak in the evap that didnt set off a code. but idk if you have that

 

yeah i have a 2.4L auto, but its worth a shot, ill look into it!

 

Silly question but you don't warm your car up in the morning do you? Cause that will waste more gas then you think.

Any smoke or misfires that haven't set a light? Stuck injector maybe? 16 is really low....

Is there a hole in the tank lol

 

Clogged cat? Which you can't go by the cluster but mine was saying 14.1 and found out my cat was clogged up.. Its ok now though i have the zzp catless 3"

 

Does catless hurt or help your mileage?

 

Not sure just yet its only been on for two days now but if we wanna go about the cluster then yeah its going Back up now lol but i run e85 so i don't get as good of gas millage to begin with. And if you get on it a lot you seem to get worse i guess because its just completely open

 

Won't really change it, but if anything make it ever so slightly better.

 

lol there is not a hole in my tank hahahha i dont have and misfires or smoke, injectors im not sure of. I do let it idle until the coolant reaches around 60~70 degrees because i dont like to run the car cold

Sadly im pretty sure that ZZP doesnt make a catless for the 2.4L LE5 :/ lol

 

You can always either cut the cat open gut it out or just cut the cat off and weld a solid pipe in place of it. Or just buy a new catted downpipe If yours was clogged

Also the only reason it would hurt your gas millage is getting on it to much...because it's sounds so orgasmic!!!

 

You cannot go by the instant on the cluster.. Go by gallons put into the tank and miles driven according to the odometer once you fill up again/ get more gas.. Ive seen as low as 6-8 MPG in my truck on instant with a scan gauge yet it returns 20+ MPG religiously based off odometer and gallons put in! And i have a shitty slow 99 ranger supercab 3.0 with 24LB injectors due to being Flex fuel ready! lol If it continues to burn up and your getting half the mileage you were once getting start digging.. Is the car kept up on basic maintenance wise? And with a modern car you can just start it up once the idle drops to regular you can just go it will be fine. Letting it sit and idle get's you 0 MPG as your not moving!

 

Yes they do

 

Exhaust leak before front o2 sensor? While cause the sensor to read lean and will dump fuel to compensate. If you have access to hpt or a scanner that can read fuel trims check your ltf and stf trims.

 

Option 2

These guys are hiding in your trunk