so, like if you're driving 40 mph, you get good mileage.

but, if you drive one miles per hour, even though your revs are one fortieth of 40 mph, you get worse miles per gallon(because you're practically idling).

so, what is the ultimate speed for maximum fuel efficiency? (2.4LT 5 speed)

I say 60, as when I am on cruise control at 60 on the interstate I get 42 mpg. I have 09 ss. Yet most of my driving is intown, so I average 21mpg.

i drive in town almost always and i get 24-27 mpg
just dont take off to "hard", and stop slow not abruptly
and on the highway 55-60 is probably best, but i took
a trip last month, and did 70-80 the whole time and still
got 28-30 mpg

I say 60, as when I am on cruise control at 60 on the interstate I get 42 mpg. I have 09 ss. Yet most of my driving is intown, so I average 21mpg.

If I set my cruise at 59 on the interstate I get 43mpg

There are many factors, such as wind condition and direction, terrain, etc. While "drafting" a semi, I have seen low 40's at 70, but for overall economy, mine seems to be in the low 60's. Find a flat open stretch of highway without much traffic (so you don't irritate the other drivers) and try setting your cruise control at 60, then bump it up after a mile or so and watch your DIC display set to instant fuel mileage. You will notice a drop in mileage every mile or so you increase. If you have an older HHR set it to avg MPG and reset it after you bump up the speed each time.

Depends on the terrain. If its pool table flat, with slight (and I mean slight) ups and downs cruise at 60 will net the best mileage. 55ish if you have some slight slopes.

There is a lot of things that you can do to get 35+mpg "intown" or in the city as I say, but I have a manual.

Truely I doubt that you can do better than 36mpg average at anyspeed using cruise.

The only way to do better is to drive it yourself. Is teh effort worth the work, you decide?

The best I've ever gotten on my 2.4 auto was 38 mpg flat terraine @ 55 mph driving across central Florida, using 87 octane. Since there seems that all gas is 10% ethanol my mileage has dropped by 10% recently. My overall average has been 30.3 mpg for nearly three years. Around town driving, I've been running a consistant 25-26 mpg.

Old Lars drive is an excellent example of pool table flat. The key is never accelerating to downshift, for hills, or passing. Tough unless you live one a limestone shelf :)

i was thinking the slower the better, but, conservation of momentum counts for something, eh?
i was coming home averaging 60 mph one night, and getting about 31 mpg, but when i sped up to 65, the gas mileage started going up, until it reached about 34.
maybe it was a tail wind? i don't know, but, slower is not necessarily better, in the grand scheme of things.

I keep to 55 mph, and have seen as high as 42.5 mpg, and this was not a flat land drive. I think I can top this number, but have not had the time to take any trips.

Im gonna say that on our '08 SS auto, the sweet spot is 63 mph, had it on cruise going from G.Rap to Mack. Isl. & got 37 mpg !!

so, what is the ultimate speed for maximum fuel efficiency?

0 MPH with the engine off.:lol::lol:

But I like the more serious previous answers too.;)
It is always nice to know I'm not doing poorly.

The guy I bought mine from said he noticed the best from 65-70mph (and it is a 2.4L, 5spd) and NEVER saw less than 27. My next door neighbor has a 2.2L auto and said that there is a steep drop >70mph. In the few tanks that I've run through mine, I'm getting about 27 with 65% city, 35% hwy and trying to keep it under 3ooo rpms for shifts.

Hope this info helps...

I came back from Cape Coral yesterday ~180 miles, DIC average speed 53, DIC said 33 mpg, refilled calculated 35.1 mpg. The DIC in my HHR has always read low. 2.4L auto. I'd say that 55 mph is a sweet spot. The car is running at 2000 rpm.

I see the best around 60MPH...

drafting..........will yield much better mpg.

I came back from Cape Coral yesterday ~180 miles, DIC average speed 53, DIC said 33 mpg, refilled calculated 35.1 mpg. The DIC in my HHR has always read low. 2.4L auto. I'd say that 55 mph is a sweet spot. The car is running at 2000 rpm.

I got my best a tick under 65. 2.4L auto here also. 32.9, but had some hills to deal with too. My actual was 33.6. Close, but not quite what you saw :-)

I came back from Cape Coral yesterday ~180 miles, DIC average speed 53, DIC said 33 mpg, refilled calculated 35.1 mpg. The DIC in my HHR has always read low. 2.4L auto. I'd say that 55 mph is a sweet spot. The car is running at 2000 rpm.

Agreed. I can post some crazy high numbers on my little 2.2l 5 speed HHR @ 55.

Reliably the best seems to be between 55 and 60. But the best I ever averaged was a little over 65 with the cruise on and having to change elevation from right at 4000 to over 10000 and then back down to about 4500, 36.9 mpg. With a 2.2l and an auto trans I feel this is very good. I've seen in the high 40's for a while but by the end of that trip it was down to 35.1. Engine speed at a specific ground speed is the biggest factor.

Drove from Middletown, Ohio to Columbus and back yesterday...filled up at the bottom of the on ramp to the highway and filled up again at the same station on the way home. Was about 190mi round trip. Avg'd 66 mph (with a stop at the airport). Had the cruise set at 70 all the way there and back. DIC suggested that I got 29.1mpg. My calculator suggested 32.5. Not too shabby for a 2.4L

Best I ever got was 48 mpg with a Tail wind pushing us along @70mph on a flat road for about 5 minutes

http://www.youtube.com/watch?v=iLyDdDWU9fU

Best I ever got was 48 mpg with a Tail wind pushing us along @70mph on a flat road for about 5 minutes

http://www.youtube.com/watch?v=iLyDdDWU9fU

Grumpee looks more like 76 - 77 MPH unless your speedo is like mine and read a bit high?

Grumpee looks more like 76 - 77 MPH unless your speedo is like mine and read a bit high?

Yeah you're right it was around 75 mph...I'd forgotten about it...we were on our family pilgramage to the Holy City of Vegas:lol:

Just a tad over 60 in warm weather, around 57 when it is colder.

I still say we need a six-speed, stretch'em just a little more, lotta turnpike for me and I like to run about 80, just don't like peggin that high on my tach

I use Ecoroute on my Garmin 265WT to see how "efficient" I am. With the cruise control set around 105 km/h the Garmin shows a 99 for my efficiency. Ecoroute was included in the software that came with my unit but may be added to some other models of their products just by downloading and installling it.

http://www.garmin.com/garmin/cms/us/services/ecoRoute

According to their news releases they are adding Ecoroute HD to the lineup of their toys. As I understand what the unit does. You plug the unit into your cars computer and it puts the data on your Garmin's screen through a Bluetooth connection.

http://ces.cnet.com/8301-31045_1-10425380-269.html

No I don't work for them or receive any compensation. Just a guy letting others know about a new product they may find helpful!!!

I keep to 55 mph, and have seen as high as 42.5 mpg, and this was not a flat land drive. I think I can top this number, but have not had the time to take any trips.
On my 2009 LT Automatic I just returned from a 200 mile trip, mostly Interstate. I saw what the instant reading was, but checked it after filling up and got 32.5 at 67 mph actual. The milage on the car showed 30.5, so you need to measure actual.

_______________________________________
2009 HHR 1LT 33,400 miles now.

^^The digital average will always be more accurate than your hand calculation. There are far to many variables in hand calculating. The pump shutoffs are always different (pump to pump), the angle of the spout effects shutoff, fuel temperature, type of fuel, decimal places held, etc. It goes on and on, unless you've modified your fuel injector tables your pcm is monitoring it far more precisely than you are calculating it.

For 63000 miles on my 06 HHR this is what my mpg statistics. The 21 is an outlier as I may have not filled the tank properly.

This was 186 tanks fill ups of gas.


Average 30.57
std dev 2.907
max 38.03
min 21.81

^^The digital average will always be more accurate than your hand calculation. There are far to many variables in hand calculating. The pump shutoffs are always different (pump to pump), the angle of the spout effects shutoff, fuel temperature, type of fuel, decimal places held, etc. It goes on and on, unless you've modified your fuel injector tables your pcm is monitoring it far more precisely than you are calculating it.

That makes pretty good sense that it could monitor better than I can figure with the tank getting refilled to different levels.

I almost always fill my tank at the same pump at the same station to about the same level of clicking every last ounce I can get in there.
I'd consider myself pretty damn good at getting as close to the same amount in there every time.
It usually is within 1/2 MPG as what the dash says.
Today I was actually surprised at it getting so close to the paper/pen/division method.

I filled it with 13.1 gallons at 431 miles with
AVG MPG at 32.8
Paper pen came to 32.9 MPG

Fuel Range was 567 Miles - Yeah baby!

9¢/mile beats the crap out of the 16¢/mile I got with the POS Eclipse
POS GSX - 100 miles cost $16
HHR SS - 100 miles costs $9
I've saved $2275 on gas with the SS and actually get to spend time driving it instead of always fixing it :one:
Also saved about $150 on oil changes.
I guess I can afford that cargo trailer (http://timeouttrailers.org/HRT.aspx) after all!

I usually drive within 5 MPH of posted speeds but let it roll as fast as it wants down steep hills unless I'm approaching a blind or populated or likely-to-be-a-cop-there area.
I usually give it a boost run or two per tank but not this time.

Must be getting old or something, I used to play the MPH game, now it's the MPG game.