I have been recently getting anywhere from 16.8-21mpg in the city, absolutely babying the car, never over 3000rpm. On the parkway doing 65-70, I was getting 26-27mpg

When the car was new, I was seeing 24-26mpg city and 34-40mpg highway...

I had new Potenzas G009's put on last week, and after that is when I noticed this decline. I don't want to place any blame on Firestone for potentially knocking something in the engine bay, but hell, they had the tire pressures at 41, 32, 31, and 37 PSI! It clearly states on the side of the tire to never exceed 40PSI, so could these imcompetent idiots have messed something else up on my car to kill my mileage?

I'm going to go out and check out the airbox and see if anything is up in there, but until then, does anyone have any suggestions?

Thanks in advance

 

Hi and welcome to winter time! Gas mileage always drops when it gets cold out. Remember fuel injected cars have no choke so the way they increase the richness of the air fuel mix is to give more fuel. That means less mpg. Relax man its no problem they all do it.

 

I understand the winter part, but this isnt the first winter with this car, I somehow survived last winter on the stock Continentals, but the mileage was never this bad, especially not a 5-10+mpg drop...If I remember correctly my winter mileage averaged around 21, much higher than what I am getting now in the 50 and 60 degrees..

 

same here man, and i am in florida, boo...i get around 18.8-19.5 city travelling...its terrible but i also figure that the traffic is just horrendous recently. a lot of just sitting there.

 

well i would make all 4 tires at the recomended psi reset your mpg gauge and drive it for a few days and see how that works.. then if your still getting the shitty mpg check your air intake and make sure your not running too rich for what you need...but besides that i dont know

 

PSI for all tires was at 30PSI yesterday as recommended...I just went out to the local highway, drove very spiritedly, and now I'm getting 23mpg...wtf?

I'm gunna go pop open the airbox and see if theres anything in there. Campo, at least you can hear a nice scream if you get on it while in traffic=]

 

Well the airfilter is fairly dirty..dirty enough to get my fingertips black...

Gunna go buy a k&n...hopefully that'll do the trick=]

 

Oh careful not to "over oil" it casue Chevy will say thats a reason to void the warrenty for the mass air sensor!

Stay away from oiled air filters! Why take the chance they'll give you crap later about it?

 

Haha I'll worry about that when I can actually find one... Strauss and NAPA don't carry the cobalt's 33-2311...I guess i'll have to wait till the Autozone near me opens soon hopefully or check out other brand-x stores tomorrow

 

tire pressure, air filter, oil filter, don't know what else could effect mpg. The cold temps will also effect it.

 

could also be the new tires, make sure they are all rotating the correct way. also, that they are the correct size. also, if they are grippier or wider than stock, it could hurt mileage.

 

Tire pressure is correct (now..), air filter is decent--being replaced by K&N soon, oil filter is good...

Everything is set with the tires, they are much grippier than the stock (but what isnt? the continentals sucked.) Same exact tire size, as well. I'll hold out and see what the new air filter does when I get it..

 

make sure your tires are the same size, if not if will affect your mpg, and if you said yout air filter is dirty enuf to turn your fingers black, theres something wrong there too, just get a stock drop in filter and check it in a week if its getting dirty fast

 

Does the car coast easily , put it in neutral on a level road and see if it bleeds off speed quick . You might have something causing resistance to the wheels :brake hangin < bearings , cv joints who knows , worth a shot

 

Coasts as good as always.

Came back to update, for whatever reason, the night I checked the air filter, my mileage has gone back to normal. Getting 25 city now and around 34-39 highway...so I don't know what happened but all is well now...

Thanks for all the ideas and input

 

I figured it may be the air filter. Did you clean it?

 

I shook and patted it out, but nothing visably came off...still waiting to get my K&N