Yeah, pretty similar across the board. If ya REALLY want to know ,reset "AVG MPG " on the DIC & switch to INST MPG for the trip.Nothing like real world, real time info ! (Also cures the "lead foot" when ya see the display say " 0 MPG" !! :lol: )

My 2010 2.2L 1LT on the display with no perceptible incline / decline and air conditioning turned off: @ 70MPH shows about 38MPG, while @ 65MPH it goes up to about 40MPG & 60MPH takes it to 41MPG, but 55MPH drops back to 38MPG & 45MPH raises it to 43MPG ??? The drop at 55 seems pretty weird but that is the car making the calculation & could be off base. This is with tires at 42PSI cold - they're rated for up to 44PSI.


My only long range trip (248 miles round trip) averaged 35.2MPG (calculated by fill-up / drive / fill-up method & not the trip computer) while cruising 65 - 70MPH for about 200 miles of the trip with the A/C running about half the time. Trip also included about 8 - 10 miles of stop & go traffic in which I typically get only 22MPG, & rest of the time was 45 - 60MPH speed.


Supposedly (I've been told by 3 different mechanics anyway), most vehicles sold in the US are factory tuned to give best mileage to performance ratio between 55 & 65 MPH, & my limited driving experience seem to hold to that statement - 1982 VW Scirrocco 5-speed manual (over 70MPH highway it did the same or worse than city mileage), 1993 Ford Escort GT 5-speed manual (over 80MPH highway it also did about same or worse than city mileage), 2001 Hyundai Accent 1.6L 3-speed auto w/OD (best MPG in it is at 58 - 60MPH), & now my HHR in which I just went over the 1000 mile mark as the current owner!


Not entirely true, at least not without the qualifier "at a given engine load"... the load on the engine plays a much bigger role in gas consumption than actual engine speed. Which is why you can keep RPM below 2000 while accelerating up to speed, but still burn a LOT more fuel than cruising along at 2000 RPM on cruise control. Likewise, if you maintain 2000 RPM going up a 10 degree incline, your MPG will go down considerably, because the increased load is trying to slow your engine down. Which is why I try to accelerate about 10MPH over limit while still on a flat before reaching such an incline, & coast up the incline for overall increased MPG. This is also why carrying extra weight in your vehicle or towing anything (I.e. added load on your engine) will always lower your MPG.

Operating the engine RPM at torque peak is where you get the best fuel economy correct? Not with this 2.4 lit. engine, because that RPM for peak torque is 4200. My 2LT, 2011 at 55 mph is turning around 2100 rpm. As a retired tool maker with GM for 30 years and a Navy Veteran as a machinist on an aircraft carrier I have had a lot of experience with all sorts of machinery. But because of all the electronics I've often wondered if a 2010-2012 Equinox six speed transmission would be a possibility? Hum, it would put the RPM at around maybe 1750. As for gas mileage it should make some difference but maybe not enough, just a thought. If there were a practical way to have a direct injected 2.5 lit. with a six speed auto transmission from an Equinox, now would be a sweet ride.

I have to question when I see some take one trip and think it means anything!

In December I went to southern Ohio I run about 60 and 65, always about 5 under on the 4 lane that is posted 65 and in places 70, state highways posted 55 I always run 60-61. anyway on the way down with a clam to 7 -10 mph headwind I averaged 34.3 mpg at the pump, and the dic seemed to agree over those miles.

Now coming home I was in front of a warm front that was blowing out of the south about 3 to 40 mph with gusts to 45,, That got me 40.8 mpg, this was driving a little faster on average coming home. I drove 196 miles on 4.8 gal. of gas. I may have gotten a little better as I really squeezed every drop in it I could for that fill up. Since my highest elevation was about mid point in my trip, I don't put much faith in what anything does at any speed, it's all about the conditions your driving ion and minor head winds will drop optimum speed for mpg drastically! Bit I do in the instant mpg the DIC tells me I'm getting. Depending on terrain, climate, and wind conditions it will never be the same all the time!

Saying that I am sure of one thing, on a winter 3000 mile average,, with warm ups till comfortable temp in the car,, 28 mpg is easy to get on 87 octane!

I hope you realize that cramming the gas tank full on a HHR is a big NO NO !
Surprised that it didn't throw a CEL.

Yep, and would not recamend this! Plus not just the HHR but most vehicles,, but on a test no big deal, and when yer gettin over 40 MPG,, one want's to be sure,, unless they just like posting big numbers, and making BS statements,,, I was positive!

That is interesting to know. Why is that?
I fill mine pretty full to get that full 420-mile range.

Of course, I remember pumping leaded blue or pink gas (over 100 octane) into my hot rods until it sprayed out around the nozzle. That's how we knew it was full (in those less eco-friendly times!) :lol:

Overfilling can cause excess gas/fumes to saturate the vent system. I think it's the canister in the back that's most prone to damage from this.

Been talked about a lot on this forum in the past. When filling up, once the nozzle clicks off, don't try to cram more in.
(topping off a little bit to the next even 10 cent amount won't hurt )

X2 what FMG says, the fuel tank if over filled , then fuel can wash back into the hose to the EVAP canister

https://i.ytimg.com/vi/Uqn5hAz_XKE/hqdefault.jpg

Exactly and why I would never recommend it, it can be a fire hazard as well! But harm to your vehicle should be warning enough.