I have been driving my 2009 HHR for 9800 miles. Throughout this I have kept the Average Fuel Economy reading up on the Driver Information Center. I reset it every time I fill up. I have always had about 22 mpg in city driving. In the last few months it has dropped to 17 mpg with no change in my driving habits. I took the car to the dealer and they said they could not find anything wrong with the fuel trims or computer codes , yet I am sure the car has dropped in fuel economy. Any ideas as to why this is happening would be appreciated.

Summer time, running the AC?

Running the A/C really makes a big MPG difference in these cars... especially in city driving. Both my SS and old 2LT lost 3-4MPG easy.

MPG is mostly dependent on driving techniques and where you ae driving. Highway driving I routinely get over 32 mpg, but around town maybe 25 mpg. I find that the DIC reads low on average MPG, so I do manual calculations. I have over 69K miles on my car and have never seen mileage below 22 mpg in the 4+ years of ownership

I would manually check it. My DIC was reading about 22-24 but when I calculated it it was more along the lines of 28-32

Check your air filter change your fuel flitr

a long with the other stuff check tire psi and tire wear and supention parts, Go back to the basics and then dig into the hard stuff. Always go start with the basics.

Did you switch fuel suppliers? I consistently get better mileage from BP fuel than from the off-brand across the street.

Check your air filter change your fuel flitr

hhr's don't have a fuel filter. the only fuel filter it uses is sock type filter on the end of the fuel pump in the tank. :thumb: The air filter is a good idea though.

hhr's don't have a fuel filter. the only fuel filter it uses is sock type filter on the end of the fuel pump in the tank.

What? Whose idea was that?

hhr's don't have a fuel filter. the only fuel filter it uses is sock type filter on the end of the fuel pump in the tank. :thumb: The air filter is a good idea though.

What? Whose idea was that?

Some "bean counter" at GM I would imagine. :roll:

Mileage can be affected by so many variables, but I have noticed that when I switch from BP to some other brand of "rocket fuel"...I see an 8-12% decrease in mileage. I used to see this back when I lived in a Sunoco heavy area and then switched to Exxon or something else...the mileage dropped a few percent. Maybe our vehicles just like a certain brand, like us "carbon based bio-modules" preferring Miller over Bud. Umm, just a thought, probably means I think too much.

when I switch from BP to some other brand of "rocket fuel"...I see an 8-12% decrease in mileage.

BP must be on to something.

Some "bean counter" at GM I would imagine. :roll:


Actually Greybeard....that change was on a employee, who was a technician, suggestion. The employee was awarded $20k for the suggestion, which was the max allowable.

The thought process, for what it is worth........

external fuel filters are no longer needed because of the design and build material of the tanks and related apparatus. It is one less part with connectors that would need to be installed (and ultimately changing). Fuels are manufactured and filtered so well at the refineries and at the tank farms that it also reduces the likelihood (the culprit here is obviously the stations.....which GM says is the responsibility of the petroleum companies to monitor).

I'm not saying I agree with it, but that's it. I knew the awardee.

Actually Greybeard....that change was on a employee, who was a technician, suggestion. The employee was awarded $20k for the suggestion, which was the max allowable.

The thought process, for what it is worth........

I'm not saying I agree with it, but that's it. I knew the awardee.

Perhaps we now know the awardee also huh Snoopy ?

Nope, not me.

I did get a couple of good sized awards for other suggestions, however. For example......

Remember when the PVC line went to the air cleaner and had a little nylon mesh type filter that was attached to the air cleaner by a metal "u" shaped clip.

Well, when you purchased a new AC replacement filter, the box also contained a new spring clip. I suggested, supplying the filter without the clip since the clip doesn't wear out. That saved GM some money, I forget what the amount was, BUT.....

I received the maximum award.

Snoopy-
I figured you had some great input somewhere in the mix. :twothumbs:

Yes I do remember the PCV metal "U" clip inside the air cleaner...

Good call, & Good for you $$..

Did the place where you buy gas switch to 10 or 15% ethanol? You will lose the same amount in mileage as the % of ethanol...My motorcycles, tractor and mower....hate the stuff!

hey have you ever noticed the fuel trucks or tankers all fill up at the same fueling station or plant to deliver your fuel in a certain part of your state lol.i myself think its b s its pretty much the same stuff maybe thiers a differnce in octane but i wouldnt doubt were getting snorked on that deal to more money more money my 2 cents

Fuel filters take the crud out of the gas tank prior to getting into the injectors or carburators. I can only imagine what the sock looks like in my 87 Fiero as the tank has never been dropped. There is a fuel filter in the gas line after the tank. That filter gets change periodically.

Frankly from what I am told, when fuel pumps are removed from the tank, NOTHING is discovered on the filters. So either the filter sock is not filtering enough and "crud" is bypassing (highly unlikely without an injector problem), or the owners were purchasing fuel from dealers and companies that do a good job.

The fuel filters that were previously installed externally, were to capture rust and other crud formed because of the metal tanks. We no longer have those tanks.

The filter sock is a secondary catch all. The primary filtering responsibility is with the retail fuel distribution network.

Realize the thread is old and topic has drifted but thought I would chime in anyway with my observations.

I drive an 06 LT with the 2.4 and automatic. Here in the frigid north with our 10-15% ethanol garbage fuel, mine varies tremendously with driving style and other factors (AC, wind etc).

I used to drive a 2007 Cobalt with the 2.2 (just got totalled, miss it!). The Cobalt was very stable mileage wise, typically getting 30 mpg on my mostly country backroad commute, and at absolute worst dropping to 25mpg while in the dead of winter being driven like I stole it.

The HHR on the other hand, will get as poor as 21mpg in the middle of winter while my wife drives it using the gas and brake as on-off switches (she chewed through the original factory ceramic pads in 25,000 miles, I got 60,000 out of mine on the Cobalt). Under optimal, laboratory like conditions in a straight cruise on the highway I can squeak 29.5mpg out of it at best.

-Dirty air filter on both cars will drop mileage 1-1.5mpg and make the engine noticeably bogged down. I can tell when its dirty without looking at it.

-At oil change time the engine starts to get louder and doesn't rev quite as smoothly. Minimal mileage drop, maybe 0.5-0.9 at most.

-Upping tire pressure from 30psi to 40psi improves mileage by up to 1mpg. This of course depends on tire quality, wear, and ride comfort preference.

-I think the 100,000 mile iridium spark plugs are a lie. On the cobalt I could feel power loss by 30,000 miles and decided to pull the plugs on it and the HHR at that time (HHR only had 15,000 or so miles at that time). On both they were already pretty well stuck into the block to the point I was afraid of stripping them taking them out, fortunately had no mishaps. All 8 plugs between them were fouled and the gaps were all over the place. After cleaning and regapping the ones in the HHR and replacing the ones in the Cobalt, the HHR idled and revved noticeably smoother and the Cobalt did also, with a noticeable improvement in power. I reinstalled the plugs with a little antiseize on the threads and dielectric grease on the coil boots so they would not seize in later on.

Overall, yes these engines are computer controlled and can run for ages without intervention, but are tuned to squeeze out every bit of economy possible and noticeably benefit from basic regular maintenance above and beyond what GM says.