[shawn672]

using a higher octane won't net you a better fuel mileage. at best you might gain some hp but its uncertain at this point. until someone gets one on a dyno we'll probably never know

 

[cruze-control]

you dont need a dyno to know if the premium fuel will make any difference. it will. its been discussed here before. i have a lot of experience with turbo cars and turbochargers in general and ive used regular on them before. never had any good results. car ran like crap, excessive knocking in the motor, and ridiculous amount of power loss. i wouldnt suggest trying it as i have lost one motor already to detonation. heres a really good explanation of what detonation is.

Detonation of Motor Fuels definition of Detonation of Motor Fuels in the Free Online Encyclopedia.

 

[shawn672]

I understand what detonation is and how higher octanes work. GM is recommending 87 octane on all cruze's. I understand higher octane might be better, but if you engine blows under 100k GM replaces it for free..


Here is an email response I've received from their engineers:

Dear Mr. Miller,

Thank you for contacting Chevrolet and for your interest in the 2011 Cruze! We appreciate the time you have taken to write us.

We are unable to provide exact measurements for the octane ratings you mentioned in your response email. The vehicle will run more efficiently with a higher octane level however this will not provide you with added power. A higher level of octane will last longer and is generally cleaner than your lower level octane. The Cruzes 1.4 ECOTEC turbo engine is equipped to run on 87 octane and we would not recommend anything higher than 91 octane. For further details please consult your local dealer for technical assistance.

 

[cruze-control]

I understand what detonation is and how higher octanes work. GM is recommending 87 octane on all cruze's. I understand higher octane might be better, but if you engine blows under 100k GM replaces it for free..


Here is an email response I've received from their engineers:

let me explain their email. see how they say the cruze is "equipped" to run on 87 octane. they use the word equipped instead of recommend because the car has a knock sensor which will dial back the timing of the motor when it detects low grade fuel. you said they are recommending 87 octane which doesnt state that in the email they sent to you. most of the older cars actually go into limp mode when they detect low grade fuel which basically just gives you enough power from your engine to "limp" home. also running anything higher than 91 is pointless for such a small turbo. now if you upgrade your turbo to something like a t67 then using a higher octane will make a difference.

yes they will replace the motor but do you think its worth all the hassle and losing the car for whatever the amount of time it takes them to diagnose the problem and put in a new motor or fix your old one. imagine if you were merging into the highway and suddenly experience detonation and the motor retards the timing which slows down the car. that can be a fatal problem if there is a car catching up to you. not trying to be a know it all but i have years of experience with modifying and tuning cars.

 

[shawn672]

You probably have more experience than I do so I'll deflect to you. Do you have a cruze yet? Did you notice any performance increase when switching to a higher octane? What did/do you use?

 

[87]

Great posts. I think I'll try out the 89 or 91. I do have one more question that I don't think I've found on here yet... can you mix different fuel grades or should you run your tank to just about empty before filling it up with a different grade of fuel?

 

[cruze-control]

You probably have more experience than I do so I'll deflect to you. Do you have a cruze yet? Did you notice any performance increase when switching to a higher octane? What did/do you use?

don't have the cruze yet. probably going to get it next year when they try to clear out the old models. so i can pick it up cheap. i did find some first hand account from owners that they did notice better throttle response when they filled it up with 91 after they got it from the dealership.

Great posts. I think I'll try out the 89 or 91. I do have one more question that I don't think I've found on here yet... can you mix different fuel grades or should you run your tank to just about empty before filling it up with a different grade of fuel?

yes you can mix different fuel grades. try avoiding running the tank empty on the turbo motor. running out of fuel while accelerating on a turbo motor is 10x worse than using low grade fuel as you will have increased air pressure due to the boost but then no combustion because of the lack of fuel. also dont try testing 89 and 91 until you fully break in the motor. i would suggest driving it on 91 for the first 500-1000 miles than do the test.

 

[70AARCUDA]

...interestingly, the USA manual states 87 octane, but, seemingly, some overseas models state 91 octane.

...anybody know *why* the difference--possibly, fuel grade or quality?

 

[CruzeChick]

So after reading this discussion, I should put 91 in my cruze when I pick it up???

 

[70AARCUDA]

...use the octane that your Owners Manual states.

 

[shawn672]

I've now gone through 2 tanks of 87 and 1 tank of 93. I did not really feel any difference?
If there is, it's minor. I need to see some numbers showing the higher octane actually helps this car at all. Until then I'm saving $5 and using 87...

 

[cruze-control]

...interestingly, the USA manual states 87 octane, but, seemingly, some overseas models state 91 octane.

...anybody know *why* the difference--possibly, fuel grade or quality?

the difference is not in the car nor the available fuel grade. its all about who they are selling the car too. they are trying to market this in north america as a really affordable sporty sedan. but they also know that recommending that consumers only use premium fuel in the cruze will deter a lot of people. remember the whole uproar about how the chevy volts were marketed to require premium fuel while everyone said they want it to use regular fuel. its the exact same scenario here. they dont want their high mpg and low budget sedan to look like a hypocrite by preaching savings but require more expensive fuel.

thankfully this way of thinking is not as widespread in other parts of the world. which is why on their manual its says the "right" fuel to use. ask anyone who has worked with turbochargers and superchargers. they will all tell you why you need to put premium fuel in your turbo car.

So after reading this discussion, I should put 91 in my cruze when I pick it up???

yes you should.

 

[70AARCUDA]

...one has to wonder, however, *how* GM can warranty the engine on 89 octane, if, as you say, 91 octane is what *should* be used.

...sorry, I'm not buying it. Granted, using 91 octane might help you gain somewhat more HP when you're drag racing, pulling a heavy maximum capacity load, or climbing through mountains fully loaded, but it is probably not necessary for the 99.9% population who drive under "normal" conditions.

...if 91 octane was required, it would've been so stated in the Owners Manual, by the GM lawyers.

 

[bpipe95]

Gm relies on knock sensors to protect the engine. In most cases they will more than protect the engine. The few that don't can conveniently be pushed into the "abuse" file.

 

[cruze-control]

...one has to wonder, however, *how* GM can warranty the engine on 89 octane, if, as you say, 91 octane is what *should* be used.

...sorry, I'm not buying it. Granted, using 91 octane might help you gain somewhat more HP when you're drag racing, pulling a heavy maximum capacity load, or climbing through mountains fully loaded, but it is probably not necessary for the 99.9% population who drive under "normal" conditions.

...if 91 octane was required, it would've been so stated in the Owners Manual, by the GM lawyers.

anyone who has enough experience with these kind of engines knows well enough that the need for a higher octane for daily driving is to prevent detonation under load. even if you dont floor the car detonation can still occur if the engine gets hot enough. like bpipe mentioned the knock sensor will retard the timing to compensate which should help protect the engine. but there will still be a few cars that the engine will go kaboom. for gm they are willing to take that hit since they will more likely lose more customers by them advertising that the cruze needs 91 octane compared to them just fixing premature engine failure when it does happen.

if you actually check one of the earlier post on this thread. there was a reply from a gm engineer and even the engineer said the same thing ive been saying. that you can use 87 octane but they recommend 91 octane.

 

[ChevyMgr]

if you actually check one of the earlier post on this thread. there was a reply from a gm engineer and even the engineer said the same thing ive been saying. that you can use 87 octane but they recommend 91 octane.

The email states it is not recommended to use any octane above 91, not that it recommends 91.

From the owners manual:

Recommended Fuel

Use regular unleaded gasoline with a posted octane rating of 87 or higher. If the octane rating is less than 87, an audible knocking noise, commonly referred to as spark knock, might be heard when driving. If this occurs, use a gasoline rated at 87 octane or higher as soon as possible. If heavy knocking is heard when using gasoline rated at 87 octane or higher, the engine needs service.
-----------------------

As cruze-control stated, conventional wisdom with a turbo has always been to use premium fuel. GM deems this to not be necessary for this engine.

You can use premium if it gives you peace of mind and you don't mind the 20¢ per gallon more coming out of your pocket, but GM states you don't have to. They stand behind that with their power train warranty.

 

[MikeyCruze]

Based on the emails from Chevy and post by ChevyMgr I will stick with 87 octane in mine and keep some of that extra money in my pocket. It doesn't bug me at all knowing I could go to a higher level. If Chevy says 87 is perfectly safe and good, I will stick with that.

 

[70AARCUDA]

...my personnal policy: 87 octane for all 'normal' driving and 91 octane if/when driving under 'loaded' conditions, ie: heavy/full weight load, or climbing through mountains, etc.

 

[Cruzer]

If the manual says 87, I am going with that.