Hi. We bought an '07 HHR (2.4l w/auto trans) back in July. Mileage has never been very good - my wife got 1 tank around 27 mpg; most are in the range of 22-24 mpg. No matter how we drive this thing, the mileage sucks compared to the EPA mileage rating and apparently the mileage others are getting.

We followed the advice of another forum and checked with the stealer where we bought the car to see if the PCM programming was the most up-to-date. It was not, so they re-flashed the PCM. I had read that updating the PCM often bumps the fuel economy up where it belongs - more in the 28-32 mpg range for highway. Heck - some of the people I've chatted with are getting more than 35 mpg in the same car.

This happened 2 weeks ago. This weekend, we had a chance to see how things were progressing. We drove about 160 miles away to see extended family. When we left, it wasn't on a full tank - had nearly 140in-town miles. Tank back home was strictly highway miles. I drove this thing like a little old man - very careful on acceleration, used the cruise control, coast up to stop lights, drove only the speed limit - mostly 70 mph, but some 55. Mileage was 22.3 hand calc'ed. The mileage coming back home was looking promising - DIC reported 31.6 mpg average econ. Needless to say, we were furious. [sm=chairshot.gif]

The car has 36k+ miles on it, and when we bought it... it was 29k miles and a certified used car - from the GM fleet. The air filter looks brand new, and we maintain it by the book. We're both 49 years old (my wife teaches school). The car is not being abused.

Any ideas what the Sam Hill is going on? I'm gonna let the stealer check it out one more time... and I'm gonna make sure they check the brakes and e-brake. If this crappy little car doesn't improve, it's gonna get readed for a Prius. Good grief - we had a full size conversion van that got nearly this mileage... and I have a 7,000 lb diesel pickup truck that gets as good or better at the same speeds!

This is ludicrous. If anyone has any suggestions... I'd love to hear them.

One other thing. This car is 100% stock, with the exception of ventshades and a bug deflector... and we only burn regular unleaded.

One more thing - does anyone know if the PCM is programmed to de-tune the engine if you don't use premium gas? We always use 87-octane; can anyone confirm (by more than just anectdote) this?

 

My '07 has the 2.2 w/auto. I can press the DIC at any time and it's always over 28. I quit driving on the highway like I had to be there righht now, and at a steady (cruise) of 60 I get 38+ on the DIC. I also live in the flatlands of he midwest, and the way this thing is geared I figure I would loose 5 MPG in the hills of Pa or NY. I lose 3-4MPG going from 60 to 70!!

 

I have a 07 2.4 and get 30 plus mpg hwy.If it is a hilly area areound 26 and up but on cruise i have seen mine as high as 35 mpg on straight aways.

 

I fill your pain, I don't know if it is the 2.4 motor or what????? it said in the owners manual to us 97 oct... i only get about 17 / 18 but I do have to say I drive like I'm going to a fire.. on the open road with cruse control I do get 30/32 mpg.... what's up....But I have to say this HHR is a ball to drive, I added an CGS air intake, what a diff. I'm getting ready to add duel ex.... whas anyone done that yet ???? what the best way custom or off the rack... please let me know.... thanks "COOLCHEVY"

 

first the dic is not very accurate second you may need to run a fuel injector cleaner in the gas, I use Lucas oil fuel injector cleaner myself. third check your tire preasures, it will make a dif.