# Premium unleaded?



## jblackburn (Apr 14, 2012)

Try 2 tanks and see what you think.

In my car, the LE2 has much better low-end response, acceleration is smoother and less jerky, MPG is slightly better, and I have had zero instances on 93 where the car suddenly pulls all power after I hear a knock from the engine.

The new 1.4T and 1.5T engines have had instances of people blowing pistons apart from LSPI. Most of those cars have been run on lower octane with lower-quality oils.


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## Eddy Cruze (Jan 10, 2014)

jblackburn said:


> The new 1.4T and 1.5T engines have had instances of people blowing pistons apart from LSPI. Most of those cars have been run on lower octane with lower-quality oils.


Do we really know that already, any links to those findings? We do know certain model year CRUZE operate fine on Regular Fuel with ambient heat being the major factor.


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## obermd (Mar 3, 2012)

I'm in the try two tanks of mid-grade (89) and then two tanks of premium (91 or higher). GM did a lot to make these engines safe to run on 87 octane, but that safety comes at the cost of overall drivability.


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## snowwy66 (Nov 5, 2017)

I don't notice any difference between 85 and 89. And will probably go back to using 85. After I've tried ethanol free first. 

Now if you want to talk oil. Then we can talk BIG difference.


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## Toocruze (Nov 26, 2017)

My build sheet says to run 91


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## nightfallgrey2018 (Nov 15, 2017)

Toocruze said:


> My build sheet says to run 91


Show me a photo of that please.


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## BU54 (Nov 24, 2014)

GM says to use 91 in my 13 cruze. I use 89 due to the high cost of 93 in my area. Around me at the stations it 87, 89, then 92 or 93. 92 or 93 is 60-70 cents more per gallon than 87 and 30-40 cents more than 89. the stations with 92-93 costs the same so in the summer I use 93 since it doesn't cost any more than 92, oh and I get about 5 more mpg with 93 vs 89.
Your results may vary.


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## chevrasaki (May 1, 2015)

For me, I tend to look at the situation logically. I spent a lot of time researching this one.

Octane is a measure of a fuel's resistance to pre-ignition (AKA Pinging, knocking, exploding too early) It's caused when the air/fuel in the cylinder reaches a condition where it spontaneously combusts. When you put a volatile substance under pressure, it increases temperature too, and it may choose to ignite all on it's own if it has enough of either heat or pressure. 87 Octane will run just fine at sea level on your average naturally aspirated car. You can even sort of get away with running 85 octane out in the midwest where the air is really thin and the atmospheric pressure is lower, though I personally wouldn't even use 85 in my lawn mower.

Turbocharged vehicles have more of both heat and pressure. The turbo is connected to the exhaust so it transfers heat to the intake air, and then it compresses it which adds more heat. It goes through an intercooler to try to remove some heat before going into the engine but the air going in is still much higher pressure than non-turbo cars. Then you mix in the gas and you shove it in a hot piston which compresses it even more, and you have to hope it doesn't explode before the spark plug can get to it.

The Cruze does indeed fall into the gray area of new cars where *91+ is* *RECOMMENDED* but it is *not REQUIRED *The car has sensors in it to monitor knocking and it will retard engine timing to fight the pre-detonation if you choose to run 87. This is where you start to see the decrease in performance. Now this is debatable. If you're the type of person who won't notice a bad wheel bearing, you probably won't notice the difference in power. If you're like me, and you live between 4,500 RPM and 6,500 RPM pushing full boost all the time then the car is going to constantly be pulling timing getting worse fuel mileage and less power while also destroying itself. If you cruise on the interstate 95% of the time, then you might just be wasting money.

Final thoughts: I run 93 octane fuel from top tier gas stations in both my vehicles that recommend them because I hate the thought of the long term harm 87 may cause. Personally I can feel a difference in the Cruze, I notice the decrease in fuel economy, and I can watch on my ultra-gauge the change in engine timing by about 5-15 degrees of advance when idle and as much as 30 degrees less of timing advance under load in boost. The engine has a shuddering almost "heart palpitation" feeling right before it pulls a lot of timing, which is what I believe to be knocking when I run 87.

Do some research, try them for yourself (it takes a few tanks for the computer to completely adjust to the fuel), do the fuel calculations, and draw your own conclusions.


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## atikovi (Dec 27, 2011)

chevrasaki said:


> The Cruze does indeed fall into the gray area of new cars where *91+ is* *RECOMMENDED* but it is *not REQUIRED *


Where did you get that from? I'm looking in my 2013 owners manual on page 9-46 under Recommended Fuel. Use regular unleaded gasoline with a posted octane rating of 87 or higher. If heavy knocking is heard when using gasoline rated at 87 octane or higher, the engine needs service.

Nowhere does it say 91+ is recommended.


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## nightfallgrey2018 (Nov 15, 2017)

I will try a few tank of premium and see if I notice any difference and will come back to report. Thanks to all who contributed to this thread.


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## jblackburn (Apr 14, 2012)

snowwy66 said:


> I don't notice any difference between 85 and 89. And will probably go back to using 85. After I've tried ethanol free first.
> 
> Now if you want to talk oil. Then we can talk BIG difference.


Minimum required is 87...do not run 85 in a turbo motor

Sent from my SM-G950U using Tapatalk


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## atikovi (Dec 27, 2011)

He must be at a high elevation where the thinner air allows lower octane gas to be used. Of course the engine puts out less power.


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## obermd (Mar 3, 2012)

nightfallgrey2018 said:


> Show me a photo of that please.


Look for KRD on the glove box sticker. If your car has the KRD code this means the engine is designed to run on 91 octane and the reason it can run on 87 is the result of a sophisticated knock sensor system and smart software to detune the engine.


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## obermd (Mar 3, 2012)

snowwy66 said:


> I don't notice any difference between 85 and 89. And will probably go back to using 85. After I've tried ethanol free first.
> 
> Now if you want to talk oil. Then we can talk BIG difference.


Don't run 85 in these engines. 85 works in naturally aspirated engines because the external air pressure is lower due to altitude, lowering combustion chamber pressures. Lower pressures are less likely to have fuel predetonation. Turbo charged engines compensate for the external air pressure drop to keep the effective altitude for the car at sea level.


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## obermd (Mar 3, 2012)

atikovi said:


> He must be at a high elevation where the thinner air allows lower octane gas to be used. Of course the engine puts out less power.


He's in the Rocky Mountains (I checked the IP address). We also have 85 octane in Denver - the Cruze was the first car I've driven that absolutely hated 85 octane. I won't put it in my Volt either even though it has a NA gas engine for on-board electric generation.


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## jblackburn (Apr 14, 2012)

atikovi said:


> He must be at a high elevation where the thinner air allows lower octane gas to be used. Of course the engine puts out less power.


Doesn't matter. 87 is the minimum required by GM. It is not tuned to run on anything lower than that, and may risk blowing apart a piston. It's in the manual.


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## Taxman (Aug 10, 2017)

atikovi said:


> He must be at a high elevation where the thinner air allows lower octane gas to be used. Of course the engine puts out less power.



But if it's turbocharged and computerized, it'll try to make full power on bad gas.


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## atikovi (Dec 27, 2011)

And then the knock sensor should cut the power, but I see what you're saying.


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## nightfallgrey2018 (Nov 15, 2017)

obermd said:


> Look for KRD on the glove box sticker. If your car has the KRD code this means the engine is designed to run on 91 octane and the reason it can run on 87 is the result of a sophisticated knock sensor system and smart software to detune the engine.


I would like to look at this sticker but there's none in the glove box. I checked in the hatch, under the panel that covers the spare tire also nothing there. Where is it located on a 2018?


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## nightfallgrey2018 (Nov 15, 2017)

I could never find the sticker anywhere on the car (I have never owned a car that didn't had a sticker before but this one has none) but I found a list of all the options in all the paperwork that the dealer provided me and the KRD option is there but has nothing beside it so don't know what that means. I will try uploading the picture of that sheet here...hoping it will work. As you will see, this is in French (my native language) but anyone can see what the codes are and when an option is on the car, there is something written beside it.


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## Merc6 (Jun 8, 2013)

nightfallgrey2018 said:


> I could never find the sticker anywhere on the car (I have never owned a car that didn't had a sticker before but this one has none) but I found a list of all the options in all the paperwork that the dealer provided me and the KRD option is there but has nothing beside it so don't know what that means. I will try uploading the picture of that sheet here...hoping it will work. As you will see, this is in French (my native language) but anyone can see what the codes are and when an option is on the car, there is something written beside it.


KRD is 91 Octane. The complete listing can be had when sending your Vin and email address to Chevy Customer Care or anyone with access to the system who wishes to come forward. Usually you just send your stuff to them and they get back to you with it. 

For my particular car, 87 didn't work out for me in the summer or the winter tuned and untuned by aftermarket support. There was an update to the ECU but that only took place in automatic cars leaving me to pretty much stay 91/93 or stall everywhere if I didn't rev past 1800 off the line. 


As for KRD, it's not marked on every car. This fleet vehicle I had didn't have it... Click if not showing pic (PB).






This was my car that hated 87 year round.


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## snowwy66 (Nov 5, 2017)

Since the beginning of time. The owners manual has ALWAYS recommended 91 octane. Now 89 or 87. 

Since the beginning of time the people have ALWAYS used the lowest octane as it's been the cheapest. And have suffered no ill effects. 

About every other year the local news runs a story on octane. And ALWAYS say there's ABSOLUTELY NO BENEFIT of running higher octane. Save your money.

Our cars are just as aspirated as non turbos. I'm guessing the reason we have them is because the engine is small these days. If you've ever ran an obd2 app. You'll know that the turbo very seldom operates unless there's a need. SUch as climbing hills with heavy pedal. The majority of the time it's all vacuum. 

Now, if you own a nissan. The CEL will come on with lower octane. I don't know if it's certain models or all models. I just know my cousin had one and that was her experience.

As for me. 85 has worked just as good as 89. And if the engine blows. It's covered for 84k miles. 

I've seen a difference with brands of oil. I haven't seen any difference in octane.


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## snowwy66 (Nov 5, 2017)

jblackburn said:


> Minimum required is 87...do not run 85 in a turbo motor
> 
> Sent from my SM-G950U using Tapatalk


Minimum required has ALWAYS been 87 or higher. LONG before the catalytic convertor came out in 1976.


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## jblackburn (Apr 14, 2012)

snowwy66 said:


> Minimum required has ALWAYS been 87 or higher. LONG before the catalytic convertor came out in 1976.


They weren't forced induction then.


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## obermd (Mar 3, 2012)

snowwy66 said:


> Since the beginning of time. The owners manual has ALWAYS recommended 91 octane. Now 89 or 87.
> 
> Since the beginning of time the people have ALWAYS used the lowest octane as it's been the cheapest. And have suffered no ill effects.


This was before the era of small turbo charged engines.



snowwy66 said:


> About every other year the local news runs a story on octane. And ALWAYS say there's ABSOLUTELY NO BENEFIT of running higher octane. Save your money.


Look at the cars they're testing - invariably they're six cylinder or larger or they're four cylinder without a turbo charger. These engines generally don't benefit from higher octane.



snowwy66 said:


> Our cars are just as aspirated as non turbos. I'm guessing the reason we have them is because the engine is small these days. If you've ever ran an obd2 app. You'll know that the turbo very seldom operates unless there's a need. SUch as climbing hills with heavy pedal. The majority of the time it's all vacuum.


Watch the boost levels in the Cruze. The Cruze generally spools up the turbo starting around 1500-1800 RPM and it's fully spooled by 2200-2500 RPM (specific engine speeds vary by trim and transmission). Even though the turbo may not be running at full tilt it is providing boost to increase the pressures in the combustion chamber. At high altitude the Cruze actually compensates for the lower air pressure by using the turbo to boost internal air pressure. Likewise anytime the engine is under load - accelerating, high speed, any RPM over 1800, etc., will cause the ECU to call for boost. Without the turbo the 1.4 engine in the Cruze is simply too underpowered to respond to the driver.



snowwy66 said:


> Now, if you own a nissan. The CEL will come on with lower octane. I don't know if it's certain models or all models. I just know my cousin had one and that was her experience.


I wish the Cruze had this warning.



snowwy66 said:


> As for me. 85 has worked just as good as 89. And if the engine blows. It's covered for 84k miles.


You're playing with fire here. On 85 octane the car is unable to completely compensate for pre-ignition by detuning the engine - it's already detuned it as much as programmed for at 87 octane. It might not be covered if the dealership tests the gas in the tank and discovers it's not at least 87 octane.


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## jblackburn (Apr 14, 2012)

^^^^^All of this.

The turbo in the Cruze is almost ALWAYS spooled.


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## obermd (Mar 3, 2012)

One other thing - product labelling Laws and Regulations in the US effectively prevent auto manufacturers from putting a "minimum" octane and a "preferred" octane. In England, the Cruze is actually listed with a minimum of 87 (MON+RON)/2 octane and preferred of 91 (MON+RON)/2 octane.


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## jblackburn (Apr 14, 2012)

Eddy Cruze said:


> Do we really know that already, any links to those findings? We do know certain model year CRUZE operate fine on Regular Fuel with ambient heat being the major factor.


https://gm.oemdtc.com/7357/17019-01...ing-cracked-piston-2016-2017-chevrolet-malibu

The 1.5T is a longer-stroke version of the LE2 that shares pistons, block, etc. Cruzes have seen similar piston failure from LSPI.


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## nightfallgrey2018 (Nov 15, 2017)

All of this is very interesting guys. I see that there is a lot of knowledgeable people on this forum and I want to thank every one of you for informing me better on this subject.

Having said this, with the info sheet that I posted, can someone tell me if KRD is deactivated (don't know how to ask this question any other way) in my 2018 Cruze? Because next to KRD it it left blank and anywhere that there is a code, take for example MF3 for 6 speed manual, T3U for fog lights etc etc so this KRD has nothing printed beside it.

All of this to say I'm very curious and my car will need a fill up on the weekend and I will fill it up with premium and try a second full tank after that to see if I noticed something different. Anyone care to answer the few question I just asked and I would be very happy about that. Thanks.


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## obermd (Mar 3, 2012)

I think KRD is a "hidden" code that's used whenever GM builds a car that uses a 91 octane rated engine that has been nested in a powertrain that detects and adjusts for knock to allow the engine to run on 87.


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## Toocruze (Nov 26, 2017)

nightfallgrey2018 said:


> Show me a photo of that please.


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## nightfallgrey2018 (Nov 15, 2017)

Toocruze said:


> View attachment 249217


KRD has nothing written beside it on my spec sheet so it means its not configured the same? Anyway...I'll put premium for a while and see how thing goes. 

Sent from my LG-H812 using Tapatalk


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## Patman (May 7, 2011)

For my 2 LTs(1.4 T) I typically run 89 with no problems. During the summer I may go to 93 but mainly 89 at least in cooler temps and non tuned. As said before try 2 tanks and see your thoughts about it, most of us have done this at least.


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## obermd (Mar 3, 2012)

atikovi said:


> Where did you get that from? I'm looking in my 2013 owners manual on page 9-46 under Recommended Fuel. Use regular unleaded gasoline with a posted octane rating of 87 or higher. If heavy knocking is heard when using gasoline rated at 87 octane or higher, the engine needs service.
> 
> Nowhere does it say 91+ is recommended.


That's because of US product labelling Laws. In the UK the same Cruze is advertised as running "87" with a note that "91" improves vehicle performance and fuel efficiency. (I put the octane numbers in quotes because Europe uses RON only while the US uses the average of RON and MON.)


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## obermd (Mar 3, 2012)

nightfallgrey2018 said:


> KRD has nothing written beside it on my spec sheet so it means its not configured the same? Anyway...I'll put premium for a while and see how thing goes.
> 
> Sent from my LG-H812 using Tapatalk


KRD is an internal GM code that identifies 91 octane engines embedded in a powertrain that compensates for 87 octane. The very fact that it's there is sufficient.


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## nightfallgrey2018 (Nov 15, 2017)

I finally found that sticker lol. It is located under the spare tire :blink:. And sure enough, there is the KRD code written. Anyway, I filled the tank with Shell Premium 91 octane last night and will report in a few weeks after I go through another full tank after that.


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## zr2s10 (Dec 8, 2017)

Hmm, I was figuring I needed new plugs at 82k, since mine has a bit of a "miss" under load. Maybe this is my issue? This is my first car with a turbo, and I've ALWAYS run 87 Octane in everything I own. I've been hesitant to try out 89 or 91, because it's sooooo much more expensive that it negates any mileage cost benefit (I get 30mpg w/6MT now). The only reason I considered buying a turbo car in the first place is because it's SUPPOSED to be okay on "regular unleaded". Several Sheetz stations near me actually offer E15, which is 88 octane, so I was considering that. E85 is obviously out of the question, but every car 2001 or newer is supposed to be okay to run E15. I've run it in my Avalanche and Grand Cherokee with no noticeable power difference. And it's actually a few cents cheaper than 87, which is E10 anyway. Has anyone tried E15 in a 1.4T ? It's kind of rare...


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## jblackburn (Apr 14, 2012)

zr2s10 said:


> Hmm, I was figuring I needed new plugs at 82k, since mine has a bit of a "miss" under load. Maybe this is my issue? This is my first car with a turbo, and I've ALWAYS run 87 Octane in everything I own. I've been hesitant to try out 89 or 91, because it's sooooo much more expensive that it negates any mileage cost benefit (I get 30mpg w/6MT now). The only reason I considered buying a turbo car in the first place is because it's SUPPOSED to be okay on "regular unleaded". Several Sheetz stations near me actually offer E15, which is 88 octane, so I was considering that. E85 is obviously out of the question, but every car 2001 or newer is supposed to be okay to run E15. I've run it in my Avalanche and Grand Cherokee with no noticeable power difference. And it's actually a few cents cheaper than 87, which is E10 anyway. Has anyone tried E15 in a 1.4T ? It's kind of rare...


It's time. Replace the plugs and be prepared for the coil pack needing to be replaced as well.

E15 runs fine in a Cruze. It might be enough to help over 87.


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## obermd (Mar 3, 2012)

zr2s10 said:


> Hmm, I was figuring I needed new plugs at 82k, since mine has a bit of a "miss" under load. Maybe this is my issue? This is my first car with a turbo, and I've ALWAYS run 87 Octane in everything I own. I've been hesitant to try out 89 or 91, because it's sooooo much more expensive that it negates any mileage cost benefit (I get 30mpg w/6MT now). The only reason I considered buying a turbo car in the first place is because it's SUPPOSED to be okay on "regular unleaded". Several Sheetz stations near me actually offer E15, which is 88 octane, so I was considering that. E85 is obviously out of the question, but every car 2001 or newer is supposed to be okay to run E15. I've run it in my Avalanche and Grand Cherokee with no noticeable power difference. And it's actually a few cents cheaper than 87, which is E10 anyway. Has anyone tried E15 in a 1.4T ? It's kind of rare...


Your plugs are due for a change. You should be ok on E15 in the Cruze - this is the federally mandated ethanol percentage for all cars since the late 1990s. Give 89 a try and see if your car performs better. We have a lot of members who run mid-grade as a pump cost/performance compromise.


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## zr2s10 (Dec 8, 2017)

jblackburn said:


> It's time. Replace the plugs and be prepared for the coil pack needing to be replaced as well.
> 
> E15 runs fine in a Cruze. It might be enough to help over 87.


So are they not rated for 100k? Or is it just better practice to do early? Also, according to CarFax the coilpack was done at 32k, lol


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## jblackburn (Apr 14, 2012)

zr2s10 said:


> So are they not rated for 100k? Or is it just better practice to do early? Also, according to CarFax the coilpack was done at 32k, lol


It was later revised in the maintenance schedules for ~60K. That seems about right from experience here. They have a habit of eroding gap more quickly than predicted.

New plugs should be set to 0.028".


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## zr2s10 (Dec 8, 2017)

jblackburn said:


> It was later revised in the maintenance schedules for ~60K. That seems about right from experience here. They have a habit of eroding gap more quickly than predicted.
> 
> New plugs should be set to 0.028".


Thanks for the tip, I'll have to pick up a set this weekend. I'm assuming I should run AC Delco Iridiums? I made the mistake of running the coppers in my truck once. That was a horrible experience. Neutered the thing. I went about 1000 miles and bought new iridiums on my next bonus day, lol


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## zr2s10 (Dec 8, 2017)

obermd said:


> Your plugs are due for a change. You should be ok on E15 in the Cruze - this is the federally mandated ethanol percentage for all cars since the late 1990. Give 89 a try and see if your car performs better. We have a lot of members who run mid-grade as a pump cost/performance compromise.


Thanks, I'll definitely change the plugs (as noted above). I'll probably switch between running E15 and 89, maybe mixed tanks. I bought this to save money on gas, it is literally paying for itself in gas money vs my truck. If I switch to 89 or 91, that cuts into it. Then my wife will cut into me...


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## obermd (Mar 3, 2012)

zr2s10 said:


> Thanks, I'll definitely change the plugs (as noted above). I'll probably switch between running E15 and 89, maybe mixed tanks. I bought this to save money on gas, it is literally paying for itself in gas money vs my truck. If I switch to 89 or 91, that cuts into it. Then my wife will cut into me...


Run two tanks of one and then two tanks of the other. Then make your decision.


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## snowwy66 (Nov 5, 2017)

Curious as to why the spark plug gaps are so small for the high energy ignition systems on cars these days. That's taking it back to 1970's era with points ignition. 8k volts. Aren't the coil packs producing 50k volts?????

The standard gap for today's ignitions sytems are usually .05 to .06


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## zr2s10 (Dec 8, 2017)

snowwy66 said:


> Curious as to why the spark plug gaps are so small for the high energy ignition systems on cars these days. That's taking it back to 1970's era with points ignition. 8k volts. Aren't the coil packs producing 50k volts?????
> 
> The standard gap for today's ignitions sytems are usually .05 to .06


I read somewhere that they started to dial those back again, because of premature ignition system failures. My truck ('03) came with ~.06 gap factory, but then the new recommended gap was ~.040. My friend works at Advance in commercial sales, and he said the same thing when I bought those plugs. Considering my Cruze had the coil pack changed at 30k, maybe they decided to change it after multiple coil pack failures on these.


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## snowwy66 (Nov 5, 2017)

zr2s10 said:


> I read somewhere that they started to dial those back again, because of premature ignition system failures. My truck ('03) came with ~.06 gap factory, but then the new recommended gap was ~.040. My friend works at Advance in commercial sales, and he said the same thing when I bought those plugs. Considering my Cruze had the coil pack changed at 30k, maybe they decided to change it after multiple coil pack failures on these.


I think the cars could handle it. But probably not for the duration originally recommended. Maybe 50k mile intervals. 

I'm a retired auto mechanic. I've seen tons of vehicles go past the 100k mark before any missfire occured.


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## jblackburn (Apr 14, 2012)

snowwy66 said:


> Curious as to why the spark plug gaps are so small for the high energy ignition systems on cars these days. That's taking it back to 1970's era with points ignition. 8k volts. Aren't the coil packs producing 50k volts?????
> 
> The standard gap for today's ignitions sytems are usually .05 to .06


N/A engines are relatively high in comparison. A Toyota, for instance, is .040". Turbocharged engines will snuff out the flame like the wind to a match at high gaps, and then you get a misfire or annoying stutter. A Cruze will do this almost as soon as the gap opens up past .035"


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## jblackburn (Apr 14, 2012)

zr2s10 said:


> Thanks for the tip, I'll have to pick up a set this weekend. I'm assuming I should run AC Delco Iridiums? I made the mistake of running the coppers in my truck once. That was a horrible experience. Neutered the thing. I went about 1000 miles and bought new iridiums on my next bonus day, lol


Coppers actually run fantastic in these engines, but maintenance (regapping) is very frequent.

The stock plugs are NGK IFR7G7 or AC Delco 41-121 (rebranded NGK).

http://www.cruzetalk.com/forum/34-gen1-1-4l-turbo/21850-hesitation-gone.html


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## obermd (Mar 3, 2012)

zr2s10 said:


> Thanks for the tip, I'll have to pick up a set this weekend. I'm assuming I should run AC Delco Iridiums? I made the mistake of running the coppers in my truck once. That was a horrible experience. Neutered the thing. I went about 1000 miles and bought new iridiums on my next bonus day, lol


The NGK BKR7E vPower coppers gapped at 0.025" are probably the best plug to run in the Cruze. You'll have to pull them out around 7-8,000 miles to regap. Then replace them after another 7-8,000 miles.


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## 17Hatch6MT (Dec 28, 2015)

I've noted what I think was LSPI two different times. I think both were after starting to use Midgrade after a few tanks of Premium. Once, the car was part warm, and I 3/4-to-floored the pedal in, maybe 3rd gear, with the engine about 2000 rpm. The second time, I 3/4-to-floored it in, not sure of the gear, 3rd or 4th, with the engine about 3000 rpm. Each time exactly the same. Rattling sound heard as much through the firewall as from under the hood, accompanied by a marked reduction in power. Lasted about 1/10 sec, not sure whether the ecm or my foot reacted first to stop it.

I tend to drive short trips. The 2nd occasion happened about 100 mi into a long trip. Didn't notice any more episodes after that, on the return leg of the trip, after about 500 mi total distance on the trips. Midgrade octane all the way. If it's O2 sensor related, does the car 'need' frequent long trips to keep the O2 sensor clean?

(edit) Oops, I think 87-89-91 octane are the common three settings around here. In the above, I originally wrote 89-91-93. Substituted the words 'Midgrade' and 'Premium'


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## 17Hatch6MT (Dec 28, 2015)

I wonder if a recent dealer oil change was to blame. They overfilled it by about 1/2 quart. The 1st LSPI incident (that I'm aware of) happened after this oil change. When I called to make an appointment to correct the overfill, the service advisor said, 'How could that have happened? It's a metered fill.' I wonder if they used bottled stuff off the shelf that may have been dis-recommended due to this issue. They did drain & refill with fresh oil (so they said) in the correct amount (I verified the dipstick reading before leaving the dealer premises this time.) The 2nd LSPI event happened 200 mi after.


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## zr2s10 (Dec 8, 2017)

I know these are small engines, but is 1/2 qt over going to really affect them? The only issues I've seen (on admittedly older cars, non-turbo) is oil burning and piston slap, but that was on a car that was WAAAAAY overfilled, lol. My brother-in-law had a Cressida that burned oil, so his dad told him to add a quart every week.... But didn't show him how to actually check the level... He called me and said his car was running funny, lol. Long story - short, We had to suction oil out through the dipstick tube, after I showed him what a dipstick was. (looked at a picture of my father-in-law)


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## 17Hatch6MT (Dec 28, 2015)

The overfill was a clue that they poured in bottles instead of using their bulk machine. Not the 1/2 quart per se. I've had it happen before at quickie lube joints that they put in the 'cheap stuff' instead of what I'd paid for. My thought was maybe they'd done this here, using up old stock instead of putting in what the manufacturer's update required. Or, simply through negligence or laziness used the wrong oil (if they would fill the wrong quantity, they might also use the wrong oil.) Older oils are blamed (apparently due to the calcium additives) for causing/exacerbating the LSPI problem. If they drained and refilled it, maybe they refilled it with the proper oil this time. So maybe won't be any more noticeable LSPI.

Love the clueless drivers. I recall stopping to help a lady with a disabled car (era before cell phones). Looked under the hood. (This was in the 70s, when you might actually hv been able to suss out a mechanical problem by looking at it.) "Where's your air filter housing?" "I took it out, is that important?" Looked at the dipstick. Nothing but sandy tar. Told her she needed a new engine.


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## zr2s10 (Dec 8, 2017)

ok, I see what you're saying now, missed the "dis-recommended" oil part before I think. 

And I could write a novel on all the stupid crap my father-in-law has done with cars, lol. Fortunately, when I met my wife, my brother-in-law was only 14. So I was able to re-train him on a few things, he actually helped (I made him, lol) on all of his car repairs that I performed. Now, he isn't an expert level mechanic by any means, but he has at least a clue. And he usually buys manuals, so he has that going for him, lol


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## snowwy66 (Nov 5, 2017)

17Hatch6MT said:


> The overfill was a clue that they poured in bottles instead of using their bulk machine. Not the 1/2 quart per se. I've had it happen before at quickie lube joints that they put in the 'cheap stuff' instead of what I'd paid for. My thought was maybe they'd done this here, using up old stock instead of putting in what the manufacturer's update required. Or, simply through negligence or laziness used the wrong oil (if they would fill the wrong quantity, they might also use the wrong oil.) Older oils are blamed (apparently due to the calcium additives) for causing/exacerbating the LSPI problem. If they drained and refilled it, maybe they refilled it with the proper oil this time. So maybe won't be any more noticeable LSPI.
> 
> Love the clueless drivers. I recall stopping to help a lady with a disabled car (era before cell phones). Looked under the hood. (This was in the 70s, when you might actually hv been able to suss out a mechanical problem by looking at it.) "Where's your air filter housing?" "I took it out, is that important?" Looked at the dipstick. Nothing but sandy tar. Told her she needed a new engine.


When i was a auto mechanic. I had a early 90's gmc pickup towed in. For a new engine. Threw 1 rod through the pan. when i pulled the pan off. NOTHING BUT TAR. The truck only had 60k miles.


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## MRO1791 (Sep 2, 2016)

nightfallgrey2018 said:


> This is getting very confusing. After reading this article https://www.digitaltrends.com/cars/why-new-cars-recommend-premium-fuel/
> 
> Yeah, G.M. say 87 octane is fine but I heard here and a few other places that 91 is better. Is this just placebo like this article says or is there TRUE and PROVEN benefits in using 91 octane in my 2018 Hatch?
> 
> I need more than someone telling me..."sure it's better". I need concrete evidence since my car is still brand new and I want to make sure it runs top at all time but I don't want to pay more for something that really isn't better in the end and just makes me feel better. Thanks for anyone having hard evidence that 91 octane is better, if not, I'll continue putting regular unleaded.


The higher octane is better, it might not be REQUIRED, but it is better. I run mid-grade or premium on my 1996 Saturn, because I measure the actual MPG in real time with the UltraGuage.. and calculate per tank MPG at the pump.. I have hard calculated that the ACTUAL increase in MPG with the higher octane fuel, saves enough fuel (MPG increase) to more than offset the higher price of the fuel, and it has noticeably more power.. that in a 21 year old, naturally aspirated engine with 200K miles.. I would expect more significant gains even with at turbo charged direct injection engine that is in the Gen 2 Cruze.. Do your own calculations, or monitor the MPG on the display.. run a couple of Premium tanks.. then go to Regular.. I think you'll find the higher octane fuel pays for itself, and will be much better for the long term health of the engine.


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## zr2s10 (Dec 8, 2017)

So I finally got around to changing my plugs. Been busy with home renovation, truck problems, lazy, etc, lol. Amazing how easy it was. Especially since #3 was loose! I had a ton of blow by, and the plug was fouled pretty bad. The others were so-so, but not horrendous. I put A/C Iridiums in it, gapped at .030. I was averaging 32 mpg in the fall, but have been getting about 30 all winter, so I would have never guessed it was that bad. But I noticed the difference as soon as I backed the car out of the garage. It has always stumbled a little in Reverse no matter how hard I tried to feather the clutch, even on a flat. 1st was less problematic, but possible to stumble as well. I just assumed it was due to it being such a small engine compared to the V6 manuals I've had before. Apparently #3 was bad since day 1 (for me)! Overall, it's got more power down low, runs smoother, and the mileage is ticking up (I'll reset it at the next tank and do a pump/trip check). I plan on checking the plugs at all oil changes now, just to be safe.

And as far as the E15 I mentioned before, it seems to run fine on it (even on a bad cylinder, lol) compared to 87. I had one tank of it that ran 28-29, but that was in the dead of winter. As temps have come up, I've tried it last two tanks, and been at 30-31. I'll see what it does on the new plugs, with warm temps, then try moving back to 87 and see what the difference is with the new plugs.


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## zr2s10 (Dec 8, 2017)

zr2s10 said:


> And as far as the E15 I mentioned before, it seems to run fine on it (even on a bad cylinder, lol) compared to 87. I had one tank of it that ran 28-29, but that was in the dead of winter. As temps have come up, I've tried it last two tanks, and been at 30-31. I'll see what it does on the new plugs, with warm temps, then try moving back to 87 and see what the difference is with the new plugs.


Well, mileage leveled off around 31. I also noticed a bit of a flat spot in the RPM range where it wasn't accelerating as hard. So I switched to 93 for 3 tanks now, and I am a believer now, lol. 35mpg, and it runs GREAT compared to anything else so far! Loving it


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## williscu (Apr 10, 2018)

Bumping old thread. Im in Pittsburgh with lots of hills. Theres a hill near my house with a 9.5% slope over a quarter mile distance with a stop sign at the top. Heres what I got in my 2012 Cruze eco Manual. Regular unleaded approached hill in 3rd gear about 35mph @ 2600 rpm. ignition timing was 18 degrees steady then down to -0 degrees (shifted into 2nd) & bogging down at top of hill. -8 degrees timing pulling off at the top of hill. Avg 30.3 mpg per tank.

Premium unld approaching same hill about 35mph @ 37 degrees timing down to +8 degrees in 3rd gear all way up to stop sign. +6 degrees pulling off from stop then back up to +24 degs timing cruise. Avg 33.5mpg per tank. The premium unleaded takes it! Double the timing at cruise & 1/3 the timing retard under load. Thats the power reduction people are complaning about. Its negative timing numbers which also overheats the cat converter.





zr2s10 said:


> Well, mileage leveled off around 31. I also noticed a bit of a flat spot in the RPM range where it wasn't accelerating as hard. So I switched to 93 for 3 tanks now, and I am a believer now, lol. 35mpg, and it runs GREAT compared to anything else so far! Loving it


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## snowwy66 (Nov 5, 2017)

Run 2 full tanks and post the numbers.

I've noticed when switching octane the computer takes a tank and a half to stabilize.

When I drop to 88non. My economy goes up then back. Switxh back to 91 and it goes down, then back.

Or maybe it's the other way around. Been awhile since I ran non ethanol.


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