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Hi, so I recently bought a Cruze, and I noticed the on the highway at least during the Fall, I was getting ~34 mpg. I read up on here about how the 1.4 L turbocharged Cruze can take advantage of higher octane fuel for better responsiveness and possibly better fuel economy, so I tried it out.

Over here we usually have "regular" = 87, "premium" = 89, and "super" = 91. Some gas stations have more options past 91 but I usually just see that.

I put premium 89 from Shell into the Cruze and my mileage apparently went from 34 mpg to 37 mpg on the highway. I filled up half the tank on Shell and later on the rest with Petro-Canada 89.

When the temp dropped to -10 C to -5C, my mileage appeared to become 32 mpg, so I filled up with regular 87 again. Mileage went down to 29 mpg. This might have something to do with ethanol blending at different stations for all I know, but basically I'm seeing a 3 mpg difference between 87 and 89 octane for me.

So for the next tank I fill up (might be a while), I was going to try super 91, possibly from Shell, and see how that goes - I'm not sure of what the impact will be during the winter but we'll see.
 

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These discussions always bring to mind the "YMMV" thought. Winter blend always gas brings a couple of MPGs less than summer blend gas. Also, driving practices and traffic bring even more variables into the mix. SWMBO's style and mine produce quite a big difference. She will get as much as 5 mpg less than me on the same route and time of day. I coast more, brake less, and accelerate more slowly than her and it shows. Our car is impervious to octane rating (proved it with live testing over a couple thousand miles), so that's one variable that is absent from our environment.
 

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Other thing to take into account is the car is used to 87 it's not going to respond to 91/93 well right out the box. It needs to see the fuel being used a few tank fills. Even more so if you still had 87 in the tank and are one of those refill when it's at half or 1/4 tank kind of person.
 

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Welcome to CruzeTalk. As Merc said it takes a tank or 2 for the computer to adjust to the new fuel mapping for higher octane bc the first tank may be a little "diluted" by the lower octane at first when switching octane levels. The car does definitely respond better to the higher octane as well as MPG. So it is one of those "trade offs" cost vs. performance.
 

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Price between grades may vary between stations especially if they are top tier listed like Shell. If and when you do switch, try and pay attention where you get it. If you live in an area where there is a string of 87 only pay inside gas stations, Shell and BP down the street aren't to be trusted. Not only do they lower the price of 87 to compete with that string of 87 only no name stations, they jack the price of 89 and 91/93 up. What usually happens is that gas stays there for soo long they eventually "pretend to run out of 87 and 89" and just sell it off at a lower price.

I only pick 4 stations at most to fill from. 2 are Shell, 1 is BP and the other is Costco. All are near the freeway of well off neighborhoods and 1 is near a BMW Land Rover dealership where the 93 button damage looks like the accurate 87 button damage at normal gas stations.

Late welcome to Cruzetalk.
 

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As others have stated, gas mileage generally goes down in the winter due to the winter gas blend and since the air is denser when its cold the engine computers compensate by adding more fuel for a clean burn.

When I first bought my cruze I was filling it with top tier 87 shell and was pretty disappointed with the performance. It would really struggle to get off the line in first gear if I didnt burn some of my clutch out keeping the engine reved. It also seemed to have very poor highway acceleration for passing and just cruising on the backroads of TN was a little annoying because I couldn't just keep 5th or 6th gear on the hills the engine would start getting loud, and I could hear piston slap and bogging unless I downshifted and put the engine over 2500 rpms.

After reading into turbo engines, compression ratios, and the cruze RPO codes I found out if your cruze glovebox code sticker has the "KRD" code listed then it requires 91+ premium fuel. I decided to buy an ultra-gauge to monitor the engines boost pressure, intake temperatures, and the timing advance. If the engine is not running well on 87, it will retard the timing. A picture of the ultra-gauge is posted below.

View attachment 174562

Sure enough, Once I switched to Shell 93 the timing advance was much higher. Then the car suddenly had decent response, I didn't have to get into the pedal as far to keep the car going, It actually had good pick up in 6th gear on the highway. The low end torque was starting to impress me. Finally the car was driving like it should. And on top of that I was averaging between 34-38 mpg now instead of 30-34. This was in the summer, it has dropped a bit now that it is winter but I still generally get over 30. Since then I have run nothing but 93, and I will continue to do so.

One other weird thing to note, I have noticed that the cruze does not produce as much boost when the air is cold. I believe this is because the computer is programmed so the engine is torque limited and doesn't produce more than 148 ft-lbs. This is likely why the trifeca works so well, all they do is raise the computers torque limit.
 

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I saw no difference between 87 and 93. When I switched back to 87, it was this past fall. The mileage dropped a little, but not much. It was about 1 mpg, which could have been attributed to driving conditions or even the weather, it had cooled off when I switched back to 87.
 

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I saw no difference between 87 and 93. When I switched back to 87, it was this past fall. The mileage dropped a little, but not much. It was about 1 mpg, which could have been attributed to driving conditions or even the weather, it had cooled off when I switched back to 87.
87 works in cooler weather because the intercooler doesn't heat soak as quickly or often. The intercooler for this car is rather small. We've had other members report they can run 87 in the winter but need to run 89 or higher in the summer.
 

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As others has stated, gas mileage generally goes down in the winter due to the winter gas blend and since the air is denser when its cold the engine computers compensate by adding more fuel for a clean burn.

When I first bought my cruze I was filling it with top tier 87 shell and was pretty disappointed with the performance. It would really struggle to get off the line in first gear if I didnt burn some of my clutch out keeping the engine reved. It also seemed to have very poor highway acceleration for passing and just cruising on the backroads of TN was a little annoying because I couldn't just keep 5th or 6th gear on the hills the engine would start getting loud, and I could hear piston slap and bogging unless I downshifted and put the engine over 2500 rpms.

After reading into turbo engines, compression ratios, and the cruze RPO codes I found out if your cruze glovebox code sticker has the "KRD" code listed then it requires 91+ premium fuel. I decided to buy an ultra-gauge to monitor the engines boost pressure, intake temperatures, and the timing advance. If the engine is not running well on 87, it will retard the timing. A picture of the ultra-gauge is posted below.

View attachment 174562

Sure enough, Once I switched to Shell 93 the timing advance was much higher. Then the car suddenly had decent response, I didn't have to get into the pedal as far to keep the car going, It actually had good pick up in 6th gear on the highway. The low end torque was starting to impress me. Finally the car was driving like it should. And on top of that I was averaging between 34-38 mpg now instead of 30-34. This was in the summer, it has dropped a bit now that it is winter but I still generally get over 30. Since then I have run nothing but 93, and I will continue to do so.

One other weird thing to note, I have noticed that the cruze does not produce as much boost when the air is cold. I believe this is because the computer is programmed so the engine is torque limited and doesn't produce more than 148 ft-lbs. This is likely why the trifeca works so well, all they do is raise the computers torque limit.
Yes, our cars are torque managed. There is actually quite a bit of head room in the turbo for extra boost. This is why my ECO MT does better at high altitude than at sea level - the lower atmospheric air pressure is successfully compensated for by the turbo.
 

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As others has stated, gas mileage generally goes down in the winter due to the winter gas blend and since the air is denser when its cold the engine computers compensate by adding more fuel for a clean burn.

When I first bought my cruze I was filling it with top tier 87 shell and was pretty disappointed with the performance. It would really struggle to get off the line in first gear if I didnt burn some of my clutch out keeping the engine reved. It also seemed to have very poor highway acceleration for passing and just cruising on the backroads of TN was a little annoying because I couldn't just keep 5th or 6th gear on the hills the engine would start getting loud, and I could hear piston slap and bogging unless I downshifted and put the engine over 2500 rpms.

After reading into turbo engines, compression ratios, and the cruze RPO codes I found out if your cruze glovebox code sticker has the "KRD" code listed then it requires 91+ premium fuel. I decided to buy an ultra-gauge to monitor the engines boost pressure, intake temperatures, and the timing advance. If the engine is not running well on 87, it will retard the timing. A picture of the ultra-gauge is posted below.

View attachment 174562

Sure enough, Once I switched to Shell 93 the timing advance was much higher. Then the car suddenly had decent response, I didn't have to get into the pedal as far to keep the car going, It actually had good pick up in 6th gear on the highway. The low end torque was starting to impress me. Finally the car was driving like it should. And on top of that I was averaging between 34-38 mpg now instead of 30-34. This was in the summer, it has dropped a bit now that it is winter but I still generally get over 30. Since then I have run nothing but 93, and I will continue to do so.

One other weird thing to note, I have noticed that the cruze does not produce as much boost when the air is cold. I believe this is because the computer is programmed so the engine is torque limited and doesn't produce more than 148 ft-lbs. This is likely why the trifeca works so well, all they do is raise the computers torque limit.
I have a data acquisition program on my PC and interfacing hardware that will allow me to monitor and save the data. I'll be able to read every message on the CAN bus and I have a file that converts the raw data into its engineering units. I just need to build my cable, when I get time. It only requires two wires, one to CAN HI and LO.
 

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I would be very interested to view this data on a nice colorful graph of some sort.
 

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I was about to start a thread to make a little report and was happy to find this one.

I drive a 2014 Chevy Cruze eco with the manual. In summer I go with 89 octane because it is only twenty cents more than 87 and gives noticable improvement to mileage and performance. In the summer I get around 32 in town, 40 all around (which is predominantly highway though) and I would say 45 highway at 70 miles an hour.

In winters I just run 87 octane after it is consistently below 40 F.

I wanted to report that I have been surprised to see that she hasn't felt under powered. I think the cold air helps keep the gas from preigniting and so there isn't that ....what do you call it...pre-ignition...or knocking. And the gas mileage is down, but I'm okay with it. I got 37 all highway at 70 miles an hour on a three hour trip, fighting a light wind 2/3 of the way. And then I got 41 coming back when I drove a bit slower because I didn't take as much of the freeway.

The 2014 1.4 turbo is built to handle 87 better I understand and that seems to be especially true in the winter. I'm pretty confident I would get no performance improvement in winter going with 89 or 91 octane. Anyone want to dispute that with me? Interested in thoughts.

thanks,
Joe

p.s. I should add that temperatures during that trip were mid to high twenties F.
 

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....
The 2014 1.4 turbo is built to handle 87 better I understand and that seems to be especially true in the winter. I'm pretty confident I would get no performance improvement in winter going with 89 or 91 octane. Anyone want to dispute that with me? Interested in thoughts.
......
I would do that too but I fear that it may take the computer some time to readjust to the lower octane fuel and may start pinging or knocking while its trying to readjust the timing. I think I'd rather just stick with my 93 octane year round and keep the timing up, it's really not that much more and the cruze is already so efficient it deserves to be treated right.

Plus my glovebox has the RPO code "KRD" which I believe means it's recommended to run 91+
Just my thoughts on the matter.
 
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I would do that too but I fear that it may take the computer some time to readjust to the lower octane fuel and may start pinging or knocking while its trying to readjust the timing. I think I'd rather just stick with my 93 octane year round and keep the timing up, it's really not that much more and the cruze is already so efficient it deserves to be treated right.

Plus my glovebox has the RPO code "KRD" which I believe means it's recommended to run 91+
Just my thoughts on the matter.
Yes to both.

My car stalls in the winter on 87 anytime traction control or stabilitrac activates. after the 1st tank of gas I haven't went bellow 89.

KRD is 91 octane but the computer detects knock from 87 and has a safe map to fall back to. At times after getting gas you feel the car trying to leave the 87 map on the 1st pull you do but will quickly revert back when knock is detected.
 

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The 2014 1.4 turbo is built to handle 87 better I understand and that seems to be especially true in the winter. I'm pretty confident I would get no performance improvement in winter going with 89 or 91 octane. Anyone want to dispute that with me? Interested in thoughts.
You live in an area with little or no elevation change. In hilly SW Wisconsin even in winter I can feel and record knock/timing pull on every hill when I attempt to run anything less than midgrade. My cruze is a 2012, but have driven a 2015 in the winter in my area with similar results.

I'm making a trip to Escanaba,MI tomorrow, even though 99% of that drive will be in the flat country you live in I still plan to fill with premium. Current prices being so low premium averages $1 a gallon less than my lifetime cost per gallon since owning the cruze in the spring of 2012.
 

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I have a '14 LTZ. I ran 87 for the first year I owned the car. I switched to premium last summer and thought I could tell a very subtle difference. I switched back to 87 out of curiosity a few months back and can't tell the difference. My MPGs have gone down a small amount but I'm certain that it's a) due to the cold and b) even it's not due to the cold, it's definitely not enough to justify the extra cost of premium, especially at places like Shell where premium is as much as $0.80 per gallon extra. We'll see if I change my mind again when it warms back up in the spring.
 

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The 14s and later have an adjusted ignition map to deal with 87 better.
 

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Very interesting thread. I am now curious if Im 'safe' to run 87 in my 12 ltz. Looks like i need to swap my edge insight monitor over from my f150 and see if I have any kr.
 

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Very interesting thread. I am now curious if Im 'safe' to run 87 in my 12 ltz. Looks like i need to swap my edge insight monitor over from my f150 and see if I have any kr.
Safe - yes, best performance - no. Our 2012's really do prefer 91 or higher octane but a lot of members have discovered that 89 is sufficient.
 
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