# 1.4 Eco - Worth running premium gas?



## Sir Fink (May 4, 2011)

What do you think?


thanks


Fink


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## cruzeman (Mar 13, 2011)

if you want a smoother running engine premium gas does help the turbo out in my experience.


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## CHEVYCRUZE RS (Mar 29, 2011)

i run 87 Octane on my Cruze however, you can run premium gas, some people say it adds horsepower and will make your engine last longer down the road. Either way your good for any gas you are willing to pay for!


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## CHEVYCRUZE RS (Mar 29, 2011)

P.S. - use Mobil 1 5w-30 oil for an even better life span


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## SilverCruzer (Nov 30, 2010)

This topic has been disucssed in great detail in previous posts.
Not sure of the posting name, but one of the discussions has an engineers perspective which is quite interesting.


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## Sir Fink (May 4, 2011)

thanks all. I will do some searching to see if I can locate those threads.


Fink


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## northvibe (May 4, 2011)

I thought a GMPP engineer told me they had the ECU set so if you did put premium in, it would take advantage of it. It all depends on the tune on the ECU... we would have to have people try a tank of 87 then 91. But the cost between those here is now over 20 cents, so it would need to show some good improvement imo. If you did an aftermarket tune then you could for sure take advantage of a higher octane.


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## SilverCruzer (Nov 30, 2010)

northvibe said:


> I thought a GMPP engineer told me they had the ECU set so if you did put premium in, it would take advantage of it. It all depends on the tune on the ECU... we would have to have people try a tank of 87 then 91. But the cost between those here is now over 20 cents, so it would need to show some good improvement imo. If you did an aftermarket tune then you could for sure take advantage of a higher octane.


Right. Many of us tried the higher octanes and compared. Some of us saw no difference in mileage, others claimed they did. Some claimed anything with a turbo needs higher octane, others said this car is engineered so it doesn't. Some said the compression requires it, others said there is a knock-supressor to compensate. Some said the knock-supressor is only a band aid to cover up an issue, others said the knock-supressor only is activated when needed.......
You get the picture.


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## northvibe (May 4, 2011)

SilverCruzer said:


> Right. Many of us tried the higher octanes and compared. Some of us saw no difference in mileage, others claimed they did. Some claimed anything with a turbo needs higher octane, others said this car is engineered so it doesn't. Some said the compression requires it, others said there is a knock-supressor to compensate. Some said the knock-supressor is only a band aid to cover up an issue, others said the knock-supressor only is activated when needed.......
> You get the picture.


hahha ya. And the problem with people testing it at home (stock) is that they may subconsciously drive different with different gas. And they wont drive the same places each tank. So its hard. But I think we can all agree if you tune for it, it would show a difference. I cant imagine a FI engine running that fantastic on 87 octane though....specially with all the E they put in it :/


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## Sir Fink (May 4, 2011)

SilverCruzer said:


> Right. Many of us tried the higher octanes and compared. Some of us saw no difference in mileage, others claimed they did. Some claimed anything with a turbo needs higher octane, others said this car is engineered so it doesn't. Some said the compression requires it, others said there is a knock-supressor to compensate. Some said the knock-supressor is only a band aid to cover up an issue, others said the knock-supressor only is activated when needed.......
> You get the picture.



I love the internet!






Fink


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## cruzeman (Mar 13, 2011)

i definitely noticed smoother acceleration with premium but maybe i was just imagining it????????????


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## 70AARCUDA (Nov 14, 2010)

...Google: '...*Placebo Affect*...' and then make _your own_ decision


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## Sir Fink (May 4, 2011)

70AARCUDA said:


> ...Google: '...*Placebo Affect*..." and then make _your own_ decision




I think perhaps assigning someone else placebo effects may not be warranted unless you know for a fact that premium makes no difference?


It sure does in my BMW.


Fink


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## DEcruze (Apr 29, 2011)

if the ecm was tuned for 87 thats all it needs.

i love seeing posts like this on the other forums:
"i put c16 (117 octane) in my car with a cold air intake and i swear i went slower."

well you will go slower. the higher the octane, the harder it is to "light" the fuel. so its harder th detonate too. 
i.e. n2o, boost, higher compression, more timing. 

you only need the MINIMUM octane the engine is tuned for.


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## Sir Fink (May 4, 2011)

What the lowest octane the engine is able to run on is not the question here.

Does the ECM advance the spark with premium or not, is the question.

With direct injection the fuel goes from 2000lb rails to 0 pressure in the cylinder, thereby getting very cold in the process. This works just like higher octane and obviates any purpose for premium in an Equinox with the LAF engine (for instance).

The 1.4 turbo is port injected and does not have that advantage, and the turbo greatly increases the effective compression ratio. Therefore, if the ECM will advance the spark timing with premium, it should make more power and mileage.

This was dramatically the case with my Honda Odyssey where it ran happily on 87 but seemed to gain 15hp or more and a couple MPG on 91. They are 10.5 or so to 1 compression BTW. The difference was not subtle. I just bought a tank of 91, and I will report back on any change.


Fink


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## cruzeman (Mar 13, 2011)

All I know is that I tried 93 and the car accelerated without the previous hesitation that I had. I will prob go back to 87 since all I do is drive on highway.


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## 70AARCUDA (Nov 14, 2010)

...a simple A|B|A test, using 87-93-87 octane fuel, will answer your question.


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## northvibe (May 4, 2011)

DEcruze said:


> if the ecm was tuned for 87 thats all it needs.
> 
> i love seeing posts like this on the other forums:
> "i put c16 (117 octane) in my car with a cold air intake and i swear i went slower."
> ...


the Cobalt SS runs on 91, but it's recommended to run at 93. The GMPP engineer I talked to even said the ECU will see and adjust some for it. But the LNF is a DI engine. I forgot that the 1.4L turbo isn't...I just assumed it was...and I find it odd that it isn't....what I find funny is they say DI is better for efficiency but when cars went to DI engines...their economy went down in real world or was the same. Easier to make power, can believe.


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## Gritts (Jan 23, 2011)

I really don't know if this is relative, but what the heck... 

When my old Grand Am (V6) started missing I took it first to an independant garage in the town where I worked at the time. They worked on it "all day" replaced a single spark plug cable and basically gave up on the car. Next day before work, I dropped it off at the local Chevy dealership (no Pontiac dealership in town). They cleaned the fuel injectors and did various other things I don't recalled and gave up on the car! So on the third day I drove the thirtyfive miles to the Pontiac dealer and was picked up by one of our service trucks because I had a job to go to. About two hours or so later I called the dealership from the road and the car was fixed.

That evening the mechanic asked me what gas I was using. I told him 93. He said don't waste my money, that the higher octane fuel contained essentially oil to increase the octane rating. Over time the oil clogged my fuel injectors and what he did was _correctly_ clean the fuel injectors and replace the one spark plug cable with the original factory wire.

Like I said, I don't know if this is relevent to today's cars, but I _never_ use anything but regular unleaded. If you do use premium fuel I suggest ocasionally running some acetone or other cleaner through the system.


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## 70AARCUDA (Nov 14, 2010)

...injector "clogging" is the reason all the car manufacturers call for use of "Top Tier" fuels because they contain at least a certain amount of "detergents" (chemical 'cleaners') which help wash away deposits before they can accumulate...but, nothing is 100% effective.

...for the _exact_ same engine, direct injection (DI) typically produces ~15% _more_ HP, ~ 10% _better_ fuel economy, and ~15% _lower_ CO2 emissions. The real increase in fuel economy comes from the same engine being able to "cruise" along using very lean A/F-mixtures (up to 16-18:1!), but only when under light loads and at full operating temperatures (cold is bad!).

...the GM-Holden cars have been using *S*park *I*gnition *D*irect *I*njection (SIDI) for years now and their website(s) have lots of GM-specific information and examples.

...here's the GM-Holden news release: http://media.gm.com/content/media/a...ile.res/MY 2010 Range Product Information.pdf


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## Sir Fink (May 4, 2011)

Redline SI-1 is the best injector cleaner on the planet IMO.


Red Line Synthetic Oil - Gasoline Fuel Additives - SI-1 Complete Fuel System Cleaner

Fink


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## DEcruze (Apr 29, 2011)

pardon my ignorance again for the generals way of doing things. there would be 2 ways that i can think of, to test for octane in the gas tank. one: the car would know somehow the content of the fuel by sampling it. two: just add timing until it knocks and then retard. does the ecm have logic for this?

again i am way late to the party.

lexus always required premium fuel because of the compression ratio.


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## DEcruze (Apr 29, 2011)

if the car would know that there is higher octane gas in the tank then yes, i would see a benefit from running premium fuel. you would see more power. 

i just dont know how/if the ecm has the logic for it. not saying its not poss, just saying that i dont know.


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## 70AARCUDA (Nov 14, 2010)

...the engine has *spark knock* detector(s) that the ECM uses to adjust its' ignition timing for...but, the ECM can only "compensate" for values within it's "map."


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## DEcruze (Apr 29, 2011)

i figured they did, my t type had them also.
if it hears knock i know the ecm will retard timing. 

but is there logic that says ok lets see how far we can push it? and then pull back if need be?

again im not trying to ruffle feathers, or start arguements, if thats how they do it, thats cool.


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## loudandproud (Apr 21, 2011)

A Chevy Cruze will NOT benefit from a higher octane alone. 93 octane Gasoline has a lower Qlhv than a 87 octane fuel. This means that thermal conversion effieceny of the engine will be reduced... resulting in LESS power. The people run higher octane fuels in turbo applications is because of thier high dynamic compression ratio and therefore high MEP/P3. High MEP/P3 increases knock risk. Running an higher octane fuel therefore allows you to run higher dynamic compression, and therefore produce more power with out knocking. If you do not increase the boost through a tune or other means you will be hurting power.

Only other reason for increase octane is poor combustion chamber flame propagation... which is not an issue with the Cruze.

The reason some NA motors make more power on race fuel is because most of these race fuels are oxygenated.


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## 70AARCUDA (Nov 14, 2010)

*Note Bene: Qlhv* = *Q* (energy) *L*ower *H*eating *V*alue, the energy content without heat recovery.


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## loudandproud (Apr 21, 2011)

Exactly... basically 87 octane has more energy per unit mass than 93... therefore when its fully combusted at stoich it has more energy released than 93. 

Everyone talks a 93 and 110 as if it will give you more power... It doesnt, it more or less lowers peak flame temps and has a lower spontaneous combustion point. 

The cruze is a motor with an aluminum head, very good heat transfer, efficent chamber design, tight quench, relatively low boost at low inlet temperatures (intercooled), and relatively low compression (9.5:1 is low for an engine of this size.)

The only time 93 would be nessacary is if you cranked up the boost or somehow otherwise raise dynamic compression (valve timing, stroker, static compression ratio etc..)


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## DEcruze (Apr 29, 2011)

in laymans terms, the higher the octane, the harder it is to get it to light. thats why you can get away with higher intake manifold pressures, nitrous, compression or advanced timing.

having those will "make" the higher octane act like 87. for lack of getting technical. 

side note, not all race fuels are oxygenated. i prefer to run c16 in my car. q16 is oxygenated. but the addetive in the fuel (mtbe) wreaks havoc on the injector nozzles. some you cant even run q16 because of it.


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## loudandproud (Apr 21, 2011)

DEcruze said:


> in laymans terms, the higher the octane, the harder it is to get it to light. thats why you can get away with higher intake manifold pressures, nitrous, compression or advanced timing.
> 
> having those will "make" the higher octane act like 87. for lack of getting technical.
> 
> side note, not all race fuels are oxygenated. i prefer to run c16 in my car. q16 is oxygenated. but the addetive in the fuel (mtbe) wreaks havoc on the injector nozzles. some you cant even run q16 because of it.


true c16 is not oxygenated... i ran it on my bike with my wetshot of nitrous. I was referring to other fuels like CAM2 and such...

And as far as knock sensors go... the engine was design NOT to knock under its standard operating range. If any knock occurs it is either contamination fuel or some sort of hot spot in the combustion chamber. The knock sensor is just a fail safe. It wont advance timing past its std set level (generally, i didnt write the algorythym for the cruze ecm though so who really knows).

But yeah you hit the nail on the head pretty much.


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## DEcruze (Apr 29, 2011)

all good! im just curious.


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## Sir Fink (May 4, 2011)

Thanks for all the info. Something is going on though. Feels smoother and a little stronger too.

I am sure it is not necessary, but necessary was never the question. The question was is it any better? And it seems to be.


Fink


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## 70AARCUDA (Nov 14, 2010)

...like I said:



70AARCUDA said:


> ...the engine has *spark knock* detector(s) that the ECM uses to adjust its' ignition timing for...but, *the ECM can only "complensate" for values within it's "map."*


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## Sir Fink (May 4, 2011)

70AARCUDA said:


> ...like I said:


Wish we knew if it can do that or not...

The BMW and Honda do.



Fink


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## Gritts (Jan 23, 2011)

Sir Fink said:


> Thanks for all the info. Something is going on though. Feels smoother and a little stronger too.
> 
> I am sure it is not necessary, but necessary was never the question. The question was is it any better? And it seems to be.
> 
> ...


 
Just don't forget the fuel injector cleaner!


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## Sir Fink (May 4, 2011)

OK, here is our experience with premium in a Cruze Eco.

Waste of time and money, don't bother. Seems a bit smoother but the mileage actually went down!

On regular 87 we went to San Diego (100 miles) and got 55mpg on cruise control. Same scenario with 91 octane, one week later with the same temp/humidity, we got 46mpg with the exact same speed and also on cruise. The computer is clearly not programmed to take advantage of higher octane gas.

Don't waste your money. Back to regular for us.

Fink


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## gfxdave99 (Feb 26, 2011)

I have run 87, 89 and 93 in my car. 

I have to say that from the butt dyno it feels better when running 93 and given that its not eating that much gas i dont mind the extra 2 bucks a fillup 

we could probably settle this by having somebody run dyno runs with the various grades.

Hmm I bet i could do some simple testing with my scangauge 

hmm hmm


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## Sir Fink (May 4, 2011)

I consider my test runs to San Diego definitive because all the conditions were the same, except for the gas grade, and the mileage dropped by 9mpg with the 91 octane gas.

I am interested in other evidence for sure, but I have settled the issue for myself.

Fink


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## Silphion (Mar 31, 2011)

It sounds to me that the reason to run higher-octane fuel is because 93 octane has less tendency to 'waste energy' than 87 octane, even though 87 has more 'energy per unit'. The Cruze is apparently very good about avoiding waisting energy, thus doesn't need the 'safety gap' that 93 octane provides.


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## Sir Fink (May 4, 2011)

Octane does one thing: prevent preignition (knock) on higher compression motors. Head design, type of injection, and engine management play a strong role in how all this interacts and whether preignition occurs.

In a turbocharged engine higher octane has the potential to allow the boost to be upped, effectively raising the compression, but the engine mgt. has to be able to adjust timing for it. Being that my car actually lost 9mpg with 91 octane, the engine mgt. clearly does not adjust for it.

Fink


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## 70AARCUDA (Nov 14, 2010)

...look-up "*the* *Hawthorne Effect*" on GOOGLE or in any good sociology text book.


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## Sir Fink (May 4, 2011)

70AARCUDA said:


> ...look-up "*the* *Hawthorne Effect*" on GOOGLE or in any good sociology text book.


Not sure what you are referring to here, but the gas mileage was being studied in both cases so any influence on behavior is moot, and I was on cruise control almost all the time at any rate. Mileage dropped by 9mpg on Premium.

Fink


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## 70AARCUDA (Nov 14, 2010)

...basically: *Hawthorne Effect = *people tend to change their normal _behaviour(s)_ toward the _expected_ _outcome(s)_ when they're aware they're being observed.


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## Big Tom (Mar 8, 2011)

My milage can change 9mpg just because of wind. Was the wind in your test exactly the same?


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## Sir Fink (May 4, 2011)

70AARCUDA said:


> ...basically: *Hawthorne Effect = *people tend to change their normal _behaviour(s)_ toward the _expected_ _outcome(s)_ when they're aware they're being observed.


Yes, I know what it is. I am just trying to understand how it applies here?

Fink


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## Sir Fink (May 4, 2011)

Big Tom said:


> My milage can change 9mpg just because of wind. Was the wind in your test exactly the same?


No significant wind on either day. 


Fink


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## 70AARCUDA (Nov 14, 2010)

...was the traffic pattern, flow and congestion identical on each trip?

...was there any change in altitude between start/stop locations?

...was there any change in vehicle load on each trip?

...did you drive differently because you expected the different octane fuel to make a difference (ie: Hawthorne Effect)?


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## Sir Fink (May 4, 2011)

70AARCUDA said:


> ...was the traffic pattern, flow and congestion identical on each trip?
> 
> ...was there any change in altitude between start/stop locations?
> 
> ...


1. yes, no congestion either time
2. no, same start and stop location
3. no, 2 people each way, same weight
4. no, I had no desire nor expectation of a given result, and was on cruise control almost all the time in both cases. In the case I went off cruise, it was for a steep section where I downshifted, driving as gently as possible while not losing speed. I did so on both trips, and in neither case was I off cruise for more than a minute or so.

Fink


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## 70AARCUDA (Nov 14, 2010)

...in that case, I'll 'hide' behind what my Statistics Professor once told me: _"...you can't tell the '*outliers*' from the '*true'* data with just a few data points."_

...hence the statement _"...three numbers, averaged = true(r) data."_


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## Sir Fink (May 4, 2011)

70AARCUDA said:


> ...in that case, I'll 'hide' behind what my Statistics Professor once told me: _"...you can't tell the '*outliers*' from the '*true'* data with just a few data points."_
> 
> ...hence the statement _"...three numbers, averaged = true(r) data."_


I think your prof. was suffering from the Hawthorne Effect...







Fink


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## Kaimumma (Apr 14, 2011)

Between Cuda always having that special one sentence saying in almost every post I read on this forum, and Fink signing his name after every reply, I gotta say guys......you're all my ohana.  This has got to be the best thread in the entire cruzetalk.com forum and I enjoy reading all the good info here.  Thanks guys!

On a more serious note, because you all sound like tech experts waiting for jobs with the Nascar pit crew, why is it we use 91+ octane on Vince's tune? I read the whole compression thing and engine management part but what if say Fink is giving good insight about his experience on regular and unleaded gas, and 87 is the way to go here. I mean obviously it is because the manual says it is. With Vince's tune, we still treat our motor with 91 and above because the electrical portion says to? I'm just confused in a sense that I would think mechanically if it's safer to use 87, why are we using 91 if it may harm?

Again this is coming from a rookie at all of this understanding here but I just want to make sure that purchasing the tune will be safe to run at 91 - 93 octane as recommended. I hope I didn't offend anyone cause if I did then you should come over to my house and have a beer.


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## Sir Fink (May 4, 2011)

What's a Vince's Tune?






Fink


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## Big Tom (Mar 8, 2011)

Kaimumma said:


> Again this is coming from a rookie at all of this understanding here but I just want to make sure that purchasing the tune will be safe to run at 91 - 93 octane as recommended. I hope I didn't offend anyone cause if I did then you should come over to my house and have a beer.


You provide the transportation, I'll bring the beer.


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## Big Tom (Mar 8, 2011)

Sir Fink said:


> What's a Vince's Tune?
> 
> 
> 
> ...


Read THIS


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## 70AARCUDA (Nov 14, 2010)

Kaimumma said:


> Between Cuda ... and Fink
> ...why is it we use 91+ octane on Vince's tune?


"Between Cuda ... and Fink" = _"...between a rock and a hard place"?_

...can't speak for Vince, but most people don't know that all EPA fuel economy tests are done using a specially formulated 91 octane gasoline, not 87 octane, unless the engine specifically requires 93 octane.


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## Skilz10179 (Mar 22, 2011)

Kaimumma said:


> Between Cuda always having that special one sentence saying in almost every post I read on this forum, and Fink signing his name after every reply, I gotta say guys......you're all my ohana.  This has got to be the best thread in the entire cruzetalk.com forum and I enjoy reading all the good info here.  Thanks guys!
> 
> On a more serious note, because you all sound like tech experts waiting for jobs with the Nascar pit crew, why is it we use 91+ octane on Vince's tune? I read the whole compression thing and engine management part but what if say Fink is giving good insight about his experience on regular and unleaded gas, and 87 is the way to go here. I mean obviously it is because the manual says it is. With Vince's tune, we still treat our motor with 91 and above because the electrical portion says to? I'm just confused in a sense that I would think mechanically if it's safer to use 87, why are we using 91 if it may harm?
> 
> Again this is coming from a rookie at all of this understanding here but I just want to make sure that purchasing the tune will be safe to run at 91 - 93 octane as recommended. I hope I didn't offend anyone cause if I did then you should come over to my house and have a beer.


Vince's tune raises the boost pressure 5+ psi or so. Stuffing a lot more air into the motor requires higher octane to prevent detonation upon compression.


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## Sir Fink (May 4, 2011)

Big Tom said:


> Read THIS


Thanks. Very interesting stuff.

Wouldn't put it on the car for love or money. I have done performance mods, including engine swaps, since before college days many years ago. Today, it's synthetic oil and a K&N for me and a nice warranty in place. I'll let the young guys be on the bleeding edge, I've done my time there.


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## Eco (May 13, 2011)

Hello gang. I'm a proud new owner of a 2011 Eco 6MT, It's got 54 miles on it, and it's quite nice!

I guess I could be considered a weekend tuner, I've had my fingers in Pro EFI, AEM, ViPEC, Cosworth Race ECU, and a multitude of GM computers.

The most recent computer I've worked with was the ME9 series from Bosch.

Now I cannot speak for the family 0 engines (what we all have) however, I can tell you that all of the recent GM ECU's that I've been in have "Hi octane-Spark" and "Lo octane-Spark" mapping.

Computers are fast enough nowadays where manufacturers rely on ignition timing retard on the fly to make the appropriate/safe changes for best vehicle to safety balance they can get.

From my experience vehicles with RECOMMENDED 87 octane, often will not hit the full timing that is in the Hi octane table. In fact they don't hit them nearly ever, they aren't designed to. 

Realize the real time interpolation b/t the tables represents a worst and best case scenario for pump gas (I believe).

Running 93 in a car recommended for 87 will at times not even run in the full Hi octane map. 

I'm not saying you'll pick up power or economy, but in my experience factory ECU's leave room for the wide variety and quality of fuel that we get. In otherwords, you're getting more timing with 93 than you are on 87 even if the car "recommends" 87 octane. I'm not saying you'll pick up any noticeable horsepower or fuel economy, all I'm saying is that the vehicle will command more timing.

Thanks for the ear gang.


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## 70AARCUDA (Nov 14, 2010)

Eco said:


> Hello gang. I'm a proud new owner of a 2011 Eco 6MT, It's got 54 miles on it, and it's quite nice!
> 
> I guess I could be considered a weekend tuner, I've had my fingers in Pro EFI, AEM, ViPEC, Cosworth Race ECU, and a multitude of GM computers.
> 
> ...


...+1.

...your comments mirror those of what Vince of *Trifecta™* has already stated.


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## cruzeman (Mar 13, 2011)

here is the answer.....the first time i put premium in car felt better but actually got the lowest mpgs with it....so since then i have been putting 89 octane in and the car accelerates fast and smooth and getting the best mpgs to date!!! so take it for what its worth....


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## Cruzemeister (Mar 22, 2011)

When gas in the US started hanging around the four dollar/gal area, I stopped even thinking about whether to run higher octane in a 87 octane tuned 4cyl (05 mitsu lancer, 10 mitsu lancer, 06 Ion, 08 Cobalt, now Cruze and wife's 10 lancer) . 
I used to frett over the non-ethanol advertised brands like Shell , before they threw in the towel under pressure too. Now that ALL GAS in the East Coast of the US is at least 10% ethanol, I started getting the discount grocery store generic gas. I've had no issues with it - and - they sell alot of gas compared to the relatively slower turnover at the Exxon's, Shell's,Sunoco's, etc. Granted, if I could afford a Vette, I'd prolly splurge on the best grade Shell. But I would also be frustrated at the ethanol content of these "best brands". It kind of trashes the whole "top quality" image. So...... unless the days of < $3 a gal come back, it's a non issue for me anymore. 
I will say that my 1.8 on 87 oct generic has as much pep and vigor as my brothers 6 cyl high compression Lincoln LS (2002). And he HAS to run premium or it knocks like a woodpecker. No better off the line than my Lil' Buggy.


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## Sir Fink (May 4, 2011)

Good info here. Thanks everybody!

Fink


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