I've got an '09 HHR LS. My mixed fuel economy average was roughly 28 MPG until the last few thousand miles. At 50k I got new tires, and anticipated a drop in fuel economy. It went down to roughly 26 mixed. I expected the mileage to gradually return to normal, though it has continued to drop. With regular fuel my average is now under 22 MPG. I have been to the mechanic and gotten a new air filter. There are no warning lights on, the computer read out is fine, my oil was recently changed, all fluid levels are fine, there is no vibration, and there are no other indications of a problem. If anyone has any theories/has had this problem before, I am eager to find a solution for this problem as it is one that is costing me money.

 

Welcome to the sight. Sorry you are experiencing a problem. I have noticed a drop in mine recently as well but I am getting close to 90K miles on mine. New spark plugs soon.

Did the issue occur as soon as you put the tires on or after? You may play with the air pressure in the tires. A pound or 2 more than Chevy suggests. Folks have experienced some better results with this. Havent added any extra wight to the vehicle? Change in fuel mixture at your favorite station? Winter grades are different. Also some have pulled the BCM-ECM fuses and reset the computers and stated that helped. You may try that.

I am sure there are others that will have suggestions. Good luck getting it resolved.

 

tire pressures
remote starting(colder weather)
winter blend fuel
cargo
change in normal driving route

winter will lower it on its own. 22mpgs is kinda low for that

but all these things end up factoring in to the fuel economy.

remote start uses fuel, takes longer to get to operating temp, winter blend of fuel is less efficient, more weight in the car like winter coats, gloves, snow brushes.

coasting to stops is huge with these cars, no jack rabbit starts

i think it should still be above 25 though.

 

Thanks for the input guys. My driving patterns have not really changed, and my tire pressure is at 30 PSI cold, and comes up to about 35 when the tires are good and warm. I don't keep much cargo in my car at all. I do not have a remote starter, I coast to stop lights and drive as though there an egg between my foot and the pedal. I am no speed demon.

Could the problem be a mis-timing with the valves of some sort? I have been told they are some sort of variable system that is controlled by a solenoid that could have become damaged or less capable than it ought to be. I don't know how true that is, if at all.

 

what tires did you get?
like everyone else is saying you use up more fuel in the colder months..try some throttle body cleaner, thats what i did to mine and my mpg improved, not a lot but helped

 

If there was any problem with a solenoid, & /or sensor it would throw the CEL on..

 

Winter blend gas seems to be good for almost a 10% drop by itself. The rest is probably a combo of new tires and lower pressures due to the cold.

 

@jerkyman45, I’m sorry to read about your drop in fuel economy with the HHR. Have you recently changed the stations in which your getting fuel?

I have read other forums that members, have mentioned when winter season comes around their fuel economy drops because of winter fuel.

Michelle, Chevrolet Customer Service

 

Should your tire pressure not be 34 cold? That may help.
The new tires. Are they all seasons or all season winter? Different rubber composition for better ice traction or performance traction make for higher rolling resistance....the softer the rubber compound the better grab, fast wear and more resistance....

 

Check the door jam, or read your manual - 30PSI is what is recommended.