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RandyTheHack -> Utterly miserable gas mileage (2/17/2008 6:21:33 PM)
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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 140 in-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?
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