Not-so-good Mileage.Please Help

[wallbngr]

It sounds like you aren't going into Lockup , Does your RPMs Kinda Match with the Speed .
When You get to hyway speed there should be an RPM drop after the Last gear shifted .
I have a 2011 W/ the 1.4 turbo and I wasn't getting as good miliage until I gapped the Plugs to .035
You have a different engine check the gap and open it to .030 and see what happens there .
You should get one of you Techs to scan the vehicle and see what its doing with Data Stream.

[sciphi]

i stay at a pretty constant 65-80mph depending on of im running late and what not lol.Currently at 2700 total miles now.

That's the reason for your poor fuel economy right there. If you're slowing down and speeding up between 65 and 80 mph a bunch of times on your commute your fuel economy will stink. The car uses a lot of gas cruising at 80 mph, and even more accelerating to reach 80 mph. Especially a 1.8 automatic that will drop gears like a stripper drops clothes.

Leave 5 minutes earlier and do your darndest to keep 65 mph. Your fuel mileage will go up.

I spent 40 miles at 55-60 mph, and got 51 mpg this morning. That included a few large hills. My average speed was ~44 mph thanks to the stops/starts at the beginning and end of the trip, and slowing down for some sheriffs rushing to calls.

[crazylegs]

That's the reason for your poor fuel economy right there. If you're slowing down and speeding up between 65 and 80 mph a bunch of times on your commute your fuel economy will stink. The car uses a lot of gas cruising at 80 mph, and even more accelerating to reach 80 mph. Especially a 1.8 automatic that will drop gears like a stripper drops clothes.

Leave 5 minutes earlier and do your darndest to keep 65 mph. Your fuel mileage will go up.

I spent 40 miles at 55-60 mph, and got 51 mpg this morning. That included a few large hills. My average speed was ~44 mph thanks to the stops/starts at the beginning and end of the trip, and slowing down for some sheriffs rushing to calls.

I believe you hit the nail on the head, Sciphi. I definitely see a large drop in mpg with my auto when exceeding 65 mph for a long period of time on my 30 mile commute to work. Keep it at 60 to 65 and use gradual accelerations when passing, for instance, and if all else is good with tranny/engine you should see an improvement.

[Aussie]

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!

This paragraph makes me think that maybe his car is downshifting when he backs off, maybe if he puts it in M6 on the freeway he may at least discover what the cause is if his economy improves and he will have something to go to his dealer with?

[ZachFools]

That's the reason for your poor fuel economy right there. If you're slowing down and speeding up between 65 and 80 mph a bunch of times on your commute your fuel economy will stink. The car uses a lot of gas cruising at 80 mph, and even more accelerating to reach 80 mph. Especially a 1.8 automatic that will drop gears like a stripper drops clothes.

Leave 5 minutes earlier and do your darndest to keep 65 mph. Your fuel mileage will go up.

I spent 40 miles at 55-60 mph, and got 51 mpg this morning. That included a few large hills. My average speed was ~44 mph thanks to the stops/starts at the beginning and end of the trip, and slowing down for some sheriffs rushing to calls.

Im not saying that i fluxuiate between 65-80mph on the 40 miles if thats what you think.i meant that some days ill stay steady at 70mph,some days at 65mph etc.on days i do stay steady at 65mph,this HIGHEST i averaged was a measly 25.6mpg.I do get what your saying though

[100InchHammer]

I get a consistant 40+ mpg avg of all driving in my 2012 Cruze 1LT, 1.4 turbo, 6spd auto. I drive the speed limit and accelerate normally.

[ZachFools]

SOLVED....Sorta..:

Ok,I drove another cruze to see what the difference was between that one and my LS.
HERES THE DIFFERENCE:

Bold parts mean important note.

2013 Cruze LS with a 1.8 6T30 Transmission:
Had only 807 total miles.
When I was on the highway,the gears shifted promptly at 2000 rpms. Once at 70 Mph, RPMs stayed steady at 2000 rpms in 6th gear.
Averaged 37mpg.

My 2012 Cruze LS with a 1.8 6T40 Transmission:
When I was on the highway,same route and all as I was with the 13,the gears shifted a little over 3000 rpms. Once at 70mph, RPMs stayed at a LITTLE OVER 3000 rpms in 6th gear.
Averaged 24mpg.

See the difference??I told my service manager about it the said he would look at it tomorrow morning.Although he doesnt know the difference between the two transmissions,surely they cant be THAT different right??This has gotta be why the MPGS are so bad on my car.Its obvious now it seems like.But thats what I came up with,what do you guys think??

[obermd]

SOLVED....Sorta..:

Ok,I drove another cruze to see what the difference was between that one and my LS.
HERES THE DIFFERENCE:

Bold parts mean important note.

2013 Cruze LS with a 1.8 6T30 Transmission:
Had only 807 total miles.
When I was on the highway,the gears shifted promptly at 2000 rpms. Once at 70 Mph, RPMs stayed steady at 2000 rpms in 6th gear.
Averaged 37mpg.

My 2012 Cruze LS with a 1.8 6T40 Transmission:
When I was on the highway,same route and all as I was with the 13,the gears shifted a little over 3000 rpms. Once at 70mph, RPMs stayed at a LITTLE OVER 3000 rpms in 6th gear.
Averaged 24mpg.

See the difference??I told my service manager about it the said he would look at it tomorrow morning.Although he doesnt know the difference between the two transmissions,surely they cant be THAT different right??This has gotta be why the MPGS are so bad on my car.Its obvious now it seems like.But thats what I came up with,what do you guys think??

Although I think you're on the right track something's still not right here. My 2012 ECO MT is at 2000 RPM at 65 MPH in 6th gear. I don't see how the 2013 LS is at 2000 RPM at the same speed. I do think your car's 3000+ RPM is an indication that your car is NOT shifting to 6th gear, however.

[jblackburn]

They changed the final drive ratios in the automatics for 2013. Lower RPMs on the highway, worse acceleration.

3000 at 80 is normal for a LS/LT 6MT or automatic.


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[ZachFools]

Although I think you're on the right track something's still not right here. My 2012 ECO MT is at 2000 RPM at 65 MPH in 6th gear. I don't see how the 2013 LS is at 2000 RPM at the same speed. I do think your car's 3000+ RPM is an indication that your car is NOT shifting to 6th gear, however.

Well,keep in mind,only the LS models have the 1.8,others have the 1.4 as well as different transmissions,like I said above,the ls I have is a 6t40 which ALL 2012 LS's have,while the 2013,has a 6t30 Tranny,and will have either one of those in the 13 LS.

But also when I put it into manual,it displays that it shifts into 6th when I upshift,and thats when it says 3000rpms@70mph.

They changed the final drive ratios in the automatics for 2013. Lower RPMs on the highway, worse acceleration.

3000 at 80 is normal for a LS/LT 6MT or automatic.

Thats understandable,but i'm at 3000@70mph.Thats not right,5 speeds usually shift at 3000@70mph,not 6 speeds.Hopefully they can agree with my hypothesis,it makes perfect sense,and I wouldnt have a single clue why else it could be.Guess I'll find out in the morning.