# Fuel octane in cruze eco 6 speed manual



## chevycruze2012 (Nov 13, 2012)

Who here is using 87 octane in their eco with the manual transmission? I'd like to switch here soon and would like to know how the eco manuals run and performance level is. Thanks 

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## bodeis (Jan 28, 2012)

Not tobe a jerk, but there are already several threads on this. You are going to get many different opinions. Try if for your self and see what you think and make a decicsion.


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## sciphi (Aug 26, 2011)

Assuming you're completely stock, run 87 for a few tanks and see how it goes. Some folks are happy, others aren't.


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## obermd (Mar 3, 2012)

Run a few tanks on 87. Pay attention to the throttle feel. If it's pulsing, switch to 89 octane for two tanks and again pay attention to the throttle. If it's still pulsing, go to 91/93 and repeat for two tanks. Pick the octane that you like the best. The engine is actually designed for 91/93 octane but the ECU will pull timing to prevent engine knock on 89 and 87 octane gas. The pulsing you feel is a side effect of the ECU protecting the engine from knock.


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## chevycruze2012 (Nov 13, 2012)

Okay cool. What I don't understand is why the eco models have a smaller gas tank than the rest of the three models. My LT had a 15.5 gallon tank and the eco has a 12.5 gallon tank. 

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## jblackburn (Apr 14, 2012)

Less weight of fuel = slightly better city fuel economy.

The tank is the same; the fuel pump assembly restricts filling to 12.6 gallons.

It also means you're at the pump more often doing the same kinda city driving. I'll take the extra tank capacity and less time at a gas station.


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## obermd (Mar 3, 2012)

You can always spend the extra time at the pump and trickle fill the final three gallons. As it is you should get 400 miles on a tank of gas even in the city without having to resort to trickle filling.


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## chevycruze2012 (Nov 13, 2012)

Im assuming someone on here already tried this?. So the fuel Pump is the reason why it's set to shut off at 12.6?

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## obermd (Mar 3, 2012)

chevycruze2012 said:


> Im assuming someone on here already tried this?. So the fuel Pump is the reason why it's set to shut off at 12.6?
> 
> Sent from AutoGuide.com Free App


http://www.cruzetalk.com/forum/57-how-library/12035-how-15-6-gallons-into-eco-mt-tank.html


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## Patman (May 7, 2011)

sciphi said:


> Assuming you're completely stock, run 87 for a few tanks and see how it goes. Some folks are happy, others aren't.


I was one of these people. I was justifying the lack of performance by the cost difference. Until one day it got hot and the car fell on its face on 87 octane. With 93 octane it is almost as if the car is tuned. There is good throttle response and the MPG goes up! Try it for yourself I surely think you will notice the diff with 93 vs 87. It is a little more money but the money will long be forgotten when you are complaining about the lack of power. Almost like I should a had a V8. So to speak!


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## alyupe11 (Jun 9, 2013)

Interesting I'm on my second tank of 87 and feel pulsating. I'll try 91 for next tank.


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## CruzeTech (Mar 23, 2012)

alyupe11 said:


> Interesting I'm on my second tank of 87 and feel pulsating. I'll try 91 for next tank.


You won't have to worry about that when you get the tune. You'll be on premium all the time. And with the tune, the pulsing is gone. I would pick it up sometimes on 91. I run Chevron premium in mine most of the time. When I'm not close to that, it's usually Shell. 


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## jblackburn (Apr 14, 2012)

CruzeTech said:


> You won't have to worry about that when you get the tune. You'll be on premium all the time. And with the tune, the pulsing is gone. I would pick it up sometimes on 91. I run Chevron premium in mine most of the time. When I'm not close to that, it's usually Shell.
> 
> 
> Sent from AutoGuide.com App


An updated stock tune for the '12's fixes throttle response/pulsing on lower octanes as well. Your dealer can run your VIN and see if there are any ECU software updates available for the car. It improved my drivability, even on premium, hugely.


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## jblackburn (Apr 14, 2012)

2013Cruze said:


> Any ECU updates for 2013 Cruzes?


Not that I know of. The 13 already has an updated tune/slightly tweaked engine.


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## 2013Cruze (Aug 4, 2012)

jblackburn said:


> Not that I know of. The 13 already has an updated tune/slightly tweaked engine.


What do you mean by tweaked engine?


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## jblackburn (Apr 14, 2012)

2013Cruze said:


> What do you mean by tweaked engine?


The LUV (2013) was given different injectors and a fuel system that would fully support the use of E85 gasoline, and it seems to handle 87 octane/ethanol a little bit better than my Cruze. It also got a slightly tweaked tune - one member on here was diving into the tables.

The LUJ was the older version that can only run up to 15% ethanol.

http://gmauthority.com/blog/guides/engines/luj/


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## chevycruze2012 (Nov 13, 2012)

jblackburn said:


> An updated stock tune for the '12's fixes throttle response/pulsing on lower octanes as well. Your dealer can run your VIN and see if there are any ECU software updates available for the car. It improved my drivability, even on premium, hugely.


Does this cost anything to have any updates done to the ECU at the dealership that you know of?


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## Chevyderek72 (May 16, 2011)

I always ALWAYS run premium. The first few tanks from new I ran 87, tried 91 (highest I can get) and never looked back. Same thing with my girlfriends lt auto. 87 is absolutely terrible for me, and to show it I would rather buy my own gas full price than get free 87 octane gas. This is in the Arizona heat so other areas might not he as effected.

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## jblackburn (Apr 14, 2012)

chevycruze2012 said:


> Does this cost anything to have any updates done to the ECU at the dealership that you know of?


Nope. 


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## chevycruze2012 (Nov 13, 2012)

Really?! So its kinda like a warranty factory setting that needs to be updated periodically?


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## jblackburn (Apr 14, 2012)

It's an update that, if available for your VIN number, they will apply to correct drivability issues under warranty. In my case, acceleration had become progressively worse to the point it was very jerky between 1500-3000 RPM no matter what type of gas I was using.

Here's the thread:
http://www.cruzetalk.com/forum/34-1-4l-turbo/11228-hesitating-93-octane.html


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## CruzeEcoBlueTopaz (Jan 5, 2012)

chevycruze2012 said:


> Who here is using 87 octane in their eco with the manual transmission? I'd like to switch here soon and would like to know how the eco manuals run and performance level is. Thanks



In terms of performance my eco 6spd MT drives the same on 87 and 91. If I had a buddy put gas in my vehicle I could not tell him which octane he used just by driving it without a lucky 50/50 guess. 

Now in terms of fuel economy thats something im currently testing. So far im 3 days into my 2 week experiment using 91 octane w/10%. On a weekly basis driving 1750 miles I average between 50 and 51mpg currently using 87 non ethanol If im able to increase my avg mpg to say 53 using the 91 I will switch. 

Im concerned about using 87 because of possible engine damage, recent disscussions about octanes has brought this to my attention. The only reason I use 87 is because its the only TOP TIER non ethanol octane available. I will not use any non top tier fuel even if it is 91 non ethanol fuel. My priority has always been top tier, non ethanol, octane. If i knew for certain 100% 87 does not cause engine damage I would stay with top tier 87 non ethanol. But if necessary I will switch.


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## oldskool (Mar 8, 2013)

The pulsing on low octane is caused by two things IMO. The power enrichment settings on a factory tune are ridiculous. I understand it's an economy car, but the 1.4t is so easy to get into boost, and the factory settings are so lean that it's totally understandable to have it surge. Running stoichiometric to about 13:1 in boost is such a bad idea. And that introduces the second cause of the surging. Running that lean in boost causes knock, the PCM compensates by pulling timing, and you get the lack of power. A basic tune will make even 87 octane feel better on an otherwise stock car.


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## obermd (Mar 3, 2012)

I put 87 into Penguin LS (yes, not an ECO but still relevant) without telling my son. Later that week he complained about the lack of acceleration on that tank of gas thinking I had gotten crap gas. Turns out I did get crap gas, as far as the Cruze is concerned.


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## weimerrj (Dec 4, 2011)

Well JB, it looks like I'll make an appointment to get my firmware checked out, I'm having surging on my Eco MT and have never needed to take it in for work since new - and take my underbody shield off before going in, since dealerships can't be trusted to obey.


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## chevycruze2012 (Nov 13, 2012)

Im having my dealer check for software updates for the ecu. My service advisor will call me to let me know what he finds out and ill share the info with all of you. I may just make a new thread about it. 

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