2011 HHR LT poor gas mileage
 

Hello,
New owner, first time poster. And temporarily obsessed with everything HHR.

After @ 500 miles of use and 44k on the odometer, I was awfully bummed to notice my gas mileage is terrible (one of the reasons I bought the HHR was because of the supposed economy). According to my calculations I'm getting 21.3 in gentle, mixed driving. And the computer is pretty close with 20.8. Not at all good.

My first thought: the air filter. To my satisfaction, it appeared as though the filter had never been touched (very dirty). I put in a new one today and we'll see...

Changing my HHR's air filter definitely lived up to it's infamous reputation.
I read the how-to here and it was a big help but would like to add a few details: after making all the necessary disconnections I tugged... and tugged. No way it was coming off. I decided to tackle the bolt holding down the leg at the left/lower/bottom of the filter housing. It's not easy to get at but disconnecting it did the trick (the bolt has found a new - and permanent - home in the glove box). Also, if you do this job, be careful of the lower lip of the filter/engine shroud. It's razor sharp. Got a nasty little paper cut after slicing through a rubber glove. Consider hitting that with some sandpaper beforehand. I put everything back together with a little petroleum jelly (great suggestion from another member) and it slid right into place.

I'll report back after a tank of gas. Hopefully the new air-filter will change things for the better.

I think you'll see a marked improvement, plugged or "super overdue" for a change air filters basically starve the engine making it less efficient as it labors to pull in an intake charge.

And yes, HHR's have the worlds most secure airboxes, this first time you change the filter it makes thoughts of stealing the Mona Lisa seem easy in comparison.;)

Welcome to the site!! go one set at a time!! next may be a good idea to clean the MAF sensor.

Hmmm... Stealing the Mona Lisa, eh? Now there's an idea... (With my luck, the Mona Lisa will suddenly go missing).

Yes I am hoping for a really, REALLY "marked" improvement. Time will tell.

Thanks Old, it's my pleasure to chime in. I'm liking my HHR. Just have to get some bugs out of it. Thanks for the suggestion re the MAF. Will follow up on that.

You're welcome, make sure you use Sensor Safe for MAF sensors and not Throttle body or carb spray!!

My 2011 is getting kind of bad mileage in this cold weather for some reason also. A new air filter improved it a bit. When I do "mixed" driving mostly local, by time 21MPG is about what I get. All highway with cruise control at 65MPH (under 2500 RPM) near 30MPG, once I go over about 2300 RPM the MPG takes a nose dive.

my 09 2.2 auto is down to 21.5 mpg right now. We have had -10* F and I have remote started my car lately for about a minute while I am walking up to it. The blizzaks don't help either. I typically lose 3-4 mpg in the middle of winter from the 26-27 mpg that I get in city driving in the summer.

Update: after 235 miles of various driving conditions but still gentle on the pedal, my mileage has gone from DIC 21.3 mpg to DIC 26.5 mpg (very good but I'm shooting for 28, maybe 29). The first time I calculated the DIC was running behind my manual calculation. This time they were both exactly equal.

The air-filter change absolutely made a difference. I also ran the tires with a few pounds of extra air. That may have helped.

Next step: clean the MAF and see what happens.

Final note: It appears the more air, the better. But it seems also there's a pattern of poor gas mileage in (very) cold weather, as mentioned in previous posts. Has anyone considered the idea of introducing warm air into the air box? That could easily be done
via the exhaust manifold.

Give it a try. Generally speaking cold air is supposed to be better. I wonder what would happen if somebody tried messing with the ambient air temp sensor. There are 2 air temp sensors, 1 ambient (near the front grille, depends on year) and 1 intake (part of the MAF)

"Give it a try. Generally speaking cold air is supposed to be better."


That's what I thought, too - that cold air is better. I'm gonna start with MAF cleaning. If I don't hit my target (28 - 29 average) after that, I'll go for it. A short section of flexible pipe from the back of the air-box straight down between the engine and manifold cover will do it. Piece of cake. If it doesn't do anything (or worse) just cover the hole in the box. We'll see...

Cold air is supposed to be better, however when it's 'very' cold, and the engine has a hard time warming up, it stays in its 'warm up' mode longer, which runs richer and isn't as fuel efficient. Its really hard for me to stay above about 22-23mpg here in Fargo when the temp is consistently below 0F

I really noticed that tonight. When leaving work I started the carwagon to warm it up. Turned on the defrost both front and back. Cleared the snow and ice. Took, at most, 10 minutes. When I got back in the carwagon my fuel average dropped like a stone - from @ 25.5 mpg (when I arrived at work) to @ 20.5 mpg upon driving away. And it never recovered all the way home. Now I know the ac compressor will run on defrost mode and the rear defrost is also a drain but the sudden, significant drop doesn't make any sense to me. It's a very gently driven 2.2. It shouldn't be THAT bad. My old Ranger with a 2.3 gets better mileage than that. It's starting to bug me. Here's a thought: a hotter thermostat maybe?

Remember that an idling engine gets 0mpg, hence the proliferation of Start/Stop systems on newer cars and trucks, plus an upcoming Federal mandate to make them standard on every U.S.market vehicle by 2016.

Letting an engine idle to warm it up will kill your average mpg, although in some circumstances, it's unavoidable.

So even if your not moving the clock is still ticking, so to speak. And the newest systems try to avoid that? I'm not sure I understand.

Basically the system that computes the instant mileage readout for the DIC looks at fuel flow, throttle opening, engine run time, and average road speed to come up with the figure displayed.

When it's just sitting there idling you're still using gas(fuel flow), and the engine is still racking up hours(run time), but you're not doing anything more than that.

Idling uses up roughly .4 to .7 gallons per hour according to GM's figures for their industrial engine equivalent to the Ecotec four.

As an experiment, the next time you're out driving, keep the instant mpg display up on the DIC, you'll see your average mpg drop slightly at a long traffic light. Because you've gone from say 26mpg down to 0mpg, and that will lower your average.

Start/Stop systems improve overall mpg in vehicles so equipped by roughly 10-15%, but the tradeoff is a lag in restarting after brief stops, and customer resistance due to the odd feeling of having the engine "stall" all the time. I've driven a BMW equipped with Start/Stop and it's a bit jarring at first when the engine dies at every stop, only to snort back to life when you lift off the brake pedal.

I see. But other than brief warming-up periods (when gas is used without moving) can that fully explain the pattern of poor gas mileage in cold weather? I'm tending towards thinking something else is also at play. Quite honestly, I've never heard of such consistently low mpg in an almost new, 2 wd, 4 cylinder vehicle in cold weather. Have you?

I don't doubt most of the numbers reported. But it runs the gamut. No consistency whatsoever. And it's disappointing to think I might have to move to Texas to get better gas mileage. No offense to Texans.

With all the low temps here lately my fuel mileage has dropped also. I remember years ago the fuel company's would change there fuel formula for winter time weather. It was know to decrease fuel mileage.
Wonder if they still do that?

I'm thinking the "terminal warm-up mode" is to blame, now that I think of it.

A hotter thermostat will just make your engine run hotter,not warm up faster. I was wondering this for a while. I'm able to get heat from the heater after driving less than a mile. I have never had a car warm up so fast,let alone a 4 banger. My mileage has dropped a couple of MPG s(coldest winter I can recall) but nothing like some of yours. Since mine warms up so fast, could this be why my mileage hasn't tanked? How fast does other warm up?

Mine warms up in 2-3 minutes. The cabin heater is not a good indicator, since water always circulates through the core so you get warm inside quicker.

I haven't done any cabin time/temp readings in mine myself. But the coolant sensor shows a nearly perfect 100 F rise in 5 minutes. For
example, starting at 23 F, after 5 minutes warm-up, the coolant sensor is 124 F. But the coolant temp display (DIC) won't show anything below 5 F. I'm suspicious that that COULD be a key to poor (very) cold weather mileage. So I'm thinking the ECM was programmed to manage gas usage but only within certain temperature perimeters. Operate below 5 F and bad things happen. Just a theory. And I'm certainly not expecting to ever know for sure whether that theory is a fact.

There's still some basic things I need to do. I put in a new air filter and increased tire pressure. That was good for a few MPG. Now I have to clean the MAF and am considering new plugs. It's just the damn weather. Since I don't have a garage (it's on the wish list), there's not much I can do - or want to do. If it isn't too cold, it's snowing. More snow forecast for this weekend. Then it finally looks like a break after that.

I saw 0 MPG gain running my tires at 34 PSI. One reason is that unless you inflate with nitrogen, 32 PSI cold = 35 PSI after driving 5 miles.