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Discussion Starter · #1 · (Edited)
This is long overdue, but better late than never I guess.

Car info:
2012 Chevy Cruze LT Automatic 1.4L
66,2xx miles
Location: TX
Regular Gas(87 oct)
No codes or warning lights

Engine Air filter changed- Jan 2015
Spark plugs gapped- This past week
Tires properly aired(bought new July 2015)

I got this car with about 30,000 miles(Sept 2013), always filled up with regular gas, performed all routine maintenance. Prior to May 2015, I would get 30-32 mpg on the highway(70-80mph) with my lead foot. End of May 2015, I took my car for a TSB regarding the negative battery cable and they performed the ECM update(Recall 14801). Following this update, my mileage took a noticeable hit. From low 30s, it dropped to high 20s(27-28 mpg on highway w/ lead foot). Until recently, I thought this was normal. After doing some reading on here, I realized the update should not have hurt my mileage and should have possibly helped it some. Driving conditions and my driving habits have basically remained the same(distance, traffic, no cruise cont).

I checked the spark plug gap this weekend and they were all around .024-.025 and I upped them to about .030. Too soon to tell if it's made a noticeable difference, but I'll get a better idea this weekend if that helps on my long distance trip.

Any thoughts on what might have caused this?
 

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Possibly. Either late 2014 or early 2015 was when I got the recall notice.
I have a 2013 cruze and got the notice too but haven't taken her in "yet" don't know if I will because your not the first that has seen worse MPG after the tune.
 

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Discussion Starter · #5 ·
Update: Been on a couple long distance drives since regapping, and there hasn't been a noticeable improvement in MPG.
 

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I just got another notice that I haven't done the tune update yet. Not sure I want to with how many that have had these problems. What does the dealer say when one reports worse MPG after these tunes?
Go fly a kite?
 

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There have been quite a few people reporting MPG loss after the update. Not sure the cause. Glad my car didn't require it.
 

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I had an average of 32 before the ECU update and now I only get 29MPG after I brought it in. But I think its more my driving style than more ECU.
 

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Hey folks, it's my first time posting here even though I enjoy browsing the forums as a fellow 2013 Cruze owner. I wanted to make an account to specifically post here for this issue. A few months ago when I first received the letter in the mail from my dealer regarding this update I was skeptical. I delayed it a couple months until my next oil change was due when my father (who is actually the shop supervisor at the dealer I bought my Cruze from) and I decided we should go ahead and update.

From that point on my mpg's have suffered just like OP's. Even putting premium fuel in no longer bumps my mpg's up like they used to and it mostly is due to this ECM update that apparently has the goal of reducing emissions in the Cruze. The sad part, even with the access my Father has to GM files, news, and updates; there is no way to rollback the update as GM wipes the old firmware from the servers so there is no way to access it.

The only option at this point, if you're willing to invest in one, is get an OBD tuner that can tinker with your settings. A good one at that. I figured I'd come here to confirm and find solace in others who have sadly made the upgrade and to warn others against having your dealer perform the update to your Cruze. Be warned my fellow Cruzers.
 

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I put 25,000 miles on since having the emissions recall done last May, I drive about 70% highway and my MPG is 1MPG higher than my 70,000 mile average before that.

With that said ever since I got this done my car will not run without lots of knock on 91E0 premium when It could run this fine before. I go out of my way now to find 93E10 premium instead, runs great on that. As bad as mine can run on 91E0 now, I have not even attempted 89 or 87 octane since the emissions recall.
 
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