Not-so-good Mileage.Please Help

[ZachFools]

Hey guys,I've been browsing the forums since I got my 2012 cruze ls back in november,but waited til now to join since I finally can ask my question,and looking forward to learning more about my cruze.

Ok,so I work at a Chevrolet dealership,i'm a car lot manager (Would never sell cars,blech),and I decided why not buy my vehichle where I work,right?So I did.
I have a 2012 Chevrolet Cruze LS base model,1.8 with the 6-speed automatic.

Got the vehicle when it only had 112 Miles,It now has 2734 miles.From the day I started driving it to this day,I have yet to break and average of 23 MPG,and I fill up to full tank everytime im on E.In all reality I only drive from work and back since the dang hours are so long (10hrs/day,6 days/week!)Which is 20 miles on the spot there and back (Total of 40 miles a day).36 of those total miles consist of nothing but highway,no heavy traffic what so ever.So I dont see why I havnt even seen a slight improvement in MPG?

And get this,since I'm the car lot manager,I can move any car I want.First I tried asking the salesman why its so bad,some say breakin 5000 miles will do it,and some are just flat out confused why it hasnt changed a bit with 3000 miles almost.

So I decided to take a same exact model cruze for a spin on my lunch,It only had 500 miles on it (Its a demo),I drove 46 miles,and no matter how I drove it,the average didnt drop any lower than 30mpgs!!
So SURELY there is something buggy about my cruze??

I took it to service,they did a calibration (Firmware?) update,and put all my tires to 35psi(Calls for all to be 35).
And still...No difference???After that,they said theres nothing else they could do?BULL.Surely theres some reason why its so bad?Theres GOTTA BE a reason why.

I'm trying to be as elaborate as possible that way I can get an answer pretty prompt, because the whole reason I finally decided to commit to payments is for the at least 35 mpg 27mpg avg im not getting.lol.

If you guys could help with any advice or anything id really appreciate it!!

PS:When I accelerate,im a snail and keep my foot on the pedal pretty stable,yet another reason Im stumped,I dont speed or anything,sometimes I even try going 60 on the hwy,but its pointless seeing as though the moment I let off I decelerate like crazy!
Thanks in advance!

[DeeCruze]

1.4 6-spd Manual saves more gas.. should have got that one

[ZachFools]

Yeah I know,but at the time we didnt have any in stock and also we were bringing in 13 models and pushin the twelves out..Not to mention based on my credit I was lucky to even get in what I have,but since theres no turning back I have to make due now,so I really need to figure this problem out

[XtremeRevolution]

Pull the spark plugs and check the gaps. Also check for discoloration (they should all be around the same). A lot of these Cruzes came with severely under-gapped plugs during certain production periods. This caused throttle lag/hesitation and poor fuel economy. Re-gap them to 0.035". If you have your dealership do it, make sure they adjust them to 0.035", NOT to 0.028" as is recommended in the service manual.

If you can, record the old gaps and post them here. If this is the issue, which it might be, you'll have at least one spark plug that is severely under-gapped. We have a tutorial in the How-To Library section that shows you how to pull the plugs yourself. It's very, very easy with this car.

If that's not the problem, then I have no idea what else it could be. GM would have to get involved. Check the plugs first.

[ZachFools]

Thanks for the reply!Yeah I know how to pull plugs and what not.Ill check em as soon as it stops snowing here and record the old gaps.
It does make sense,since it seems like it decelerates ridiculously quick as well.
So the cruze calls for .028",but I should put them at .035"?
Hopefully this could be the problem,I cant think of what else it could be either.Im gonna do it sometime later today

[obermd]

OP has an LS and the service manual has always said 0.028" for this engine. Go with 0.028" on the spark plug gap.

You're basically getting the city EPA estimate. If your car has an average speed indicator, can you post that value. This will help us determine if you're spending a lot of time at slower speeds than you realize. Also, have you tried the manual-matic mode of the transmission. My understanding is that this mode really helps fuel economy as it prevents the car from aggressively downshifting while coasting.

Also, don't idle to warm up the car. The Cruze simply doesn't have large enough of an engine for idling to warm up the car anyway.

[Patman]

Kinda sounds like it is getting stuck in a lower gear. Does the car shift all the way up to 6th gear? What are the RPMS when driving? Just a thought. Since the car is so quiet, you may not notice that the RPMs are high.

[spacedout]

Kinda sounds like it is getting stuck in a lower gear. Does the car shift all the way up to 6th gear? What are the RPMS when driving? Just a thought. Since the car is so quiet, you may not notice that the RPMs are high.

he could put the shifter in manual mode & see what gear he is in at any moment.

[ZachFools]

Ok,I was about to re gap my plugs?So which gap will for sure help my milelage?
And I havnt tried using the manual shifter really all that much.
My "Average" speed says im going 60 for the most part when I fill up

[obermd]

Go with the 0.028". That is the gap that has always been listed for the 1.8 engine in the LS.

Average speed should be lower - I drive 30 miles each way with most of it at 55 or 65 MPH and my average speed is in the low to mid 40s on most fill ups. I do agree with Patman that it sounds like your car may not be shifting up. What is your RPM at 60 MPH?