Hi Folks, I had a long drive in flat country this weekend, so I did some gas mileage checks along the way. Man are these HHR's touchy when it comes to highway fuel economy! All checks were made with the windows up, A/C off, and cruise control on. 93 octane. 50 degree temps.

At 60 mph it did a steady 35 mpg. To me, this is fantastic.
At 70 mph it would do 29-30 mpg. About it's EPA highway rating.
At anything over 74, it lost 1 mpg for each additional 1 mph! Ouch.
Also, at highway speeds any nudge of the pedal would cause the instant mpg's to plummet.

If the A/C was turned on, the mileage dropped one to two mpg's at speed.

I am thinking that above 70 mph the aerodynamics are really getting into the picture big-time.

My old Mercury with a V-8 would haul down 26 mpg at just about any highway speed. It didn't seem to vary much at all.

I am seeing that the HHR's mileage responds to a huge degree upon driving style and speed on the highway.

God Bless, Marc

I take mine on a 3 1/2 hour trip monthy and set cruise at 78-79 and average any were from 30 to 32mpg. Ive taken it slower, due to weather, and got almost 40 average. Then again I notice you have the 2lt so the 2.4 mines 2.2 dont know if that has much to do with it but maybe a little

I think those blanked-out side window panels must cheat the wind better..... ;) I am glad you are getting great mileage. My tires are at 35psi, and going harder would no doubt help, but I hate a hard ride. Also I have the GMPP intake. I didn't check the mileage before I added it, so I don't know if it helped. Yes, Elvis is a 2.4 liter.

I rented several Cobalts for Louisiana runs (all 2.2's), and those would get 35 to 37 highway with the air on and three folks in the car. That is what led me to buy an HHR, it's the Cobalt "wagon".

God Bless, Marc

Hey Marc,

I Have Yet to Try and See What My Mileage Actually Is! Not to sure if the Display of 17.6 Miles per Gallon is Correct But if so I'm Glad We Did the 140 Speedo Install :lol:!

Since I have installed the GMPP intake I have considered it unfair to check my in-town mileage.......vroooooom. :D God Bless, Marc

Ok, my stock 2.4L (w/Mobil full syn) in town is getting a steady 26mpg on 93 octane. And on the super-slab, cruise set to 75mph, shows 31 mpg.

Our windshields are laid back pretty good to cut wind, imo.

Imagine what an old box van would get ??

depending on how I drive I get high 20s in town my max achieved in town is 32mpg. I couldnt really believe it till I caculated it out and sure enough 32 and only done that once normally right at around 28-29mpg.

You're doing better than I am. I guess I better get an egg under my right foot. ;-) God Bless, Marc

Yeah I checked out ecomodders.com and they have a lot of advice and techniques mostly geared to a manuel, wish I had one. Any ways they have a lot of mods to improve mileage as wheel most I will never do as it looks tacky some times but will be trying a few I think.

I take mine on a 3 1/2 hour trip monthy and set cruise at 78-79 and average any were from 30 to 32mpg. Ive taken it slower, due to weather, and got almost 40 average. Then again I notice you have th 2lt so the 2.4 mines 2.2 dont know if that has much to do with it but maybe a little

That's absolutely incredible. Seriously. You probably got lucky with an ultra-perfect tuned engine. Have you written GM any letters about this? I'm sure they would pounce on something like this for their promos.

Since I have installed the GMPP intake I have considered it unfair to check my in-town mileage.......vroooooom. :D God Bless, Marc

Recently installed the GMPP CAI, My mileage went up about 1 MPG, I'm averaging around 30.5 MPG now :thumb:

Marcruger....

The aerodynamics was discussed about 1-2 years ago, on this forum. If I remember correctly ChvyMgr. posted it was something like .32. I think that's just a little over the C6, for example.

Personally I don't believe the aerodynamics are the real culprit here. I think it's more the nature of the engine. Remember, these are 4 cylinders with little torque. Once they are above the 2400-2500 RPM range they're starting on the downward curve of maximum efficiency. Watch your tach, when driving 65+, when moving in 5 mph increments.

Additionally, the combination of engine and "gearing" has a lot to do with it.

I would venture to say, after all my suspension mods are complete. My mpg may drop a bit, I'd attribute this mainly due to a probable increase in pressure on the Right long pedal..


Snoopy-

I'm impressed by the aerodynamic comparison to: ' I think that's just a little over the C6'. WOW!

& would concur about engine & gearing having a lot to do with it as well..

Maybe ChvyMgr will see this tomorrow and either confirm or correct it.

A fast search yielded this recent thread.....

http://chevyhhr.net/forums/showthread.php?t=18894&highlight=aerodynamics

I did a 300 mile trip to my dad's old house a couple of weeks ago. Cruise set at 75 on highway, A/C used probably half the trip, 85% highway. 10% secondary highway, 50-60 mph. I got 34.2 mpg.

On a second note, I refilled yesterday and got the worse tank I've ever gotten, mostly to/from work and around home. 23.x.....

Though I don't necessarily agree with driving 55, here is a website that will explain the relationship between the increase in speed, with the commensurate increase in drag and the need for increased horsepower, which means more fuel. Usually 60 mph is your point of best mpg before it really starts going downhill.

The HHR is a fairly slick little vehicle, especially compared to my Jeep Commander, but everything is difficult to push through the air when you increase speed. Not to mention don't discount headwinds, crosswinds, tailwinds, etc., when you are comparing your instant and average mpg's. Wind does play a part.

http://drive55.org/content/view/60/6/

Though I don't necessarily agree with driving 55, here is a website that will explain the relationship between the increase in speed, with the commensurate increase in drag and the need for increased horsepower, which means more fuel. Usually 60 mph is your point of best mpg before it really starts going downhill.

The HHR is a fairly slick little vehicle, especially compared to my Jeep Commander, but everything is difficult to push through the air when you increase speed. Not to mention don't discount headwinds, crosswinds, tailwinds, etc., when you are comparing your instant and average mpg's. Wind does play a part.

http://drive55.org/content/view/60/6/


I do the drive 55 thing, and it has paid me back in spades. Aurora, CO to Amarillo, TX. 440.2mi, 10.364 gallons used. I netted 42.5 mpg out of that stretch, and that was with the vehicle fully loaded with the rear seats down, front to back, and floor to ceiling, and keeping A/C use to a bare minimum. Setting the cruise control on the highway and camping out in the right lane to let the rest of the world pass by in its permanent hurry easily keeps me on the 40 mpg threshold. :cool:

With my ride, my instant gauge is now showing about 41mpg for a 1 hr drive cruising at 70. Around town I am getting about 25mpg with my 2.4.

Of course I have some mods (GMPP Intake, Cobalt GMPP exhaust manifold w/ some more porting, modded ecm, Cobalt SS rear springs). I think the most performance I 'felt' gain was the exhaust manifold and the intake. I think I will need to tune my pcm soon though to get the most of it. Getting off the line still feels a little slow at least for first gear.

BTW looking at other forums the C6 cDa is 6.16 and the HHR similar rival (the xB) is 7.7cDa.

BTW looking at other forums the C6 cDa is 6.16 and the HHR similar rival (the xB) is 7.7cDa.

Pretty cool right ?

I haven't really paid that much attention to my mileage. However, I am going to drive from Borger (about 50 miles North of Amarillo) to Rockport (50 miles East of Corpus Christi) in January. I will post some mileage notes then.

Hi Folks, The idea of getting on the backside of the torque curve makes sense to me. Since the engine isn't running at its optimum, and the aerodynamic drag increases, it makes sense that the mileage would plummet. Given that, I wonder where the 2.2 mileage falls off versus the 2.4? I wonder if the more powerful 2.4 torque is offset by the smaller displacement burning fuel in the 2.2 at higher speeds? Yes, engineering school does this to your brain. I'd love for one of the HHR development engineers to join this forum. :-) God Bless, Marc

Your observations are correct...
I have done similar tests over the years, and I can get almost 40MPG if you stay at 55 MPH with Interstate Driving. I have done the Exhaust and Air Intake mods which made the additional difference. Where I live, we burn a different fuel commonly knows as "Atlanta Blend", and we get less MPG. Once I purchase fuel outside of my state, I get better MPG. I bet without the 10% Alcohol mixture, we would do even better.

Roger that Keith. My problem is that if I drive anywhere at 55 around here I would probably get rear-ended, and most assuredly would get rude gestures and screaming. ;) Easing into Wilmington last weekend I did get to run steady at about 59 mph for a short, flat stretch and the instant mileage went way up to 34mpg (pretty good I thought!).

For a couple of years they made us run gas-a-hol here in the winter, citing 10% better winter emissions. Finally someone realized that if it gets 10% better emissions, but 30% worse gas mileage, you are on the losing team. I had a 5.0 Mustang at the time and I literally took it to the repair shop the first month to find the gas leak.

God Bless, Marc

Took a trip in Eastern Oklahoma yesterday to look at the foliage in the Ouchita Mountains. Drove about 300 miles total. Some fairly flat roads, some curvy and twisty, and some mild mountains. Averaged 27.9 for the trip. Didn't think this was too bad since ther was so much up and down, and never at one speed for too long.

Hey Marc,

Though I can appreciate good gas mileage, and one reason why I bought the HHR, I realized I can burn through enough gas in a day on one of the planes I fly to last an HHR for awhile. A B-25 we used to fly would burn around 120-130 gallons per hour, (though you had 1,700 hp each side). Ouch! Glad I wasn't paying the fuel bill on that one. Kinda' puts things into perspective with cars that get good gas mileage.

Roger that Marty. A friend who owns a P-51 once told me his actual cost per hour on his bird in maintenance, fuel, oil, rebuild kitty, etc. Needless to say I didn't ask him for a free ride. Whew. As my friend P-51 wartime pilot Mac once told me, the Mustang was intended to haul four or six .50 caliber machine guns over Germany, fight, and come home. I guess overall economy wasn't a top priority, even though it did have better range than some others. God Bless, Marc

Now I'm not sure what anyone else thinks but I tend to think a six-speed would help quite a bit, I commonly run turn-pike for work and at 80 an extra gear would be really handy, not a fan of buzzing 4 to 5 so I have to back her down and run about 60-65

Or a five-speed automatic! God Bless, Marc

Bert Baker just came out with the DD7, 7 speed..

Opss!! Wrong forum..

Marc,

My friend with the Mustang and Corsair charges $1000.00/hour for a ride in the P-51, which is relatively cheap. Lots of gas and wear and tear. I have been blessed by many rides in the P-51. I am glad I am not paying the bills! When I can figure it out I will post a picture of a formation ride I recently went on.

At those prices I'll bet he isn't including rebuild-cost-per-hour on either of those two magnificent engines. You have a really good friend to take you riding! :-) God Bless, Marc

No doubt. However, when he decided to do an overhaul on the Merlin he chose to keep it as a showpiece at his museum and put a completely new overhaul back in the Mustang. A core engine is worth about $70,000.00, so it is like having a $70,000.00 door stop.

The first website is for the museum and the second is more of an unofficial website of his museum, you can see his plane, as well as my L-2 'Looking For Trouble" in the pictures.

http://www.aircombatmuseum.org/

This link will show my L-2 toward the bottom of the page:

http://www.aeroknow.com/GALLERY/L-2ACM-gal.htm

Sadly I wouldn't have bought mine with an automatic, and as happy as I am with it, I still won't. For me automatics go to te big guns like our drag truck or a heavy 4x4, even my 4x4 ranger was a 5-speed, I'm not knockin auto's or those who prefer, it's purely my preference so an extra gear would be nice.

Ok, my stock 2.4L (w/Mobil full syn) in town is getting a steady 26mpg on 93 octane. And on the super-slab, cruise set to 75mph, shows 31 mpg.

Our windshields are laid back pretty good to cut wind, imo.

Imagine what an old box van would get ??

My last car was a 1986 Vanagon...
At 70 MPH, all buttoned up, non-functional AC off, I could sometimes do 20MPG on a cruise. That's on the stock, 2.1L 4cyl, 95 HP engine. And that is 3 over EPA.
I love my HHR, I can finally accelerate up hill.

Marty-an uncle of mine used to own B-25s.Over the course of his life,he had 3 of them.Before he died,he sold his last one(a B-25J) to General William Lyons out in California,whose pilot said that it was the nicest flying B-25 he'd ever encountered.

I am thinking that above 70 mph the aerodynamics are really getting into the picture big-time.



I don't know if the formula is the same for cars as it is buses and RVs, but I heard that for every mile an hour above 65, the wind resistance is not quite 3 times as much. So going from 65 to 75 would increase the resistance over 30 times. Not to mention aerodynamics are tricky. If you look at old RVs, they have slanted windshields, but new ones are almost straight up and down and yet are more aerodynamic. I definately think the HHR looks a bit boxy to the eye, but when it comes to airflow it is anything but.

I took a road trip from bluffton to cinncinati and kept it under 60 with the ac I got 40 mpg.

I HAVE AN 06 2LT THE BEST i EVER GOT ON THE FRWY WAS 28MPG WHEN I ADDED THE CGS INTAKE I WAS GETTING INTOWN 19 IT KEEPS GOING DOWN THIS LAST WEEK IM GETTING 16.4 NOT GOING OVER 35 MPH I THINKING I BETTER HAVE THE COMPUTOR FLASHED AT THE DEALER COST $92.00 WILL GET THIS DONE NEXT WEEK AND SEE IF IT INPROVES. IT RUNS GREAT, WHEN I HAD A PANTERA I COULD CRUIZE AT 135 MPH AND GET 34MPG

before you do that remove the ECM fuse for a few minutes to reset everything and see what happens......its like a reboot