slowion2

because the LSJ is a force induction engine and your octane rating is in direct correlation to how much knock you may encounter, and in turn how much timing you can advance "safely" along with keeping detonation at bay.

lol you guys must make these threads almost once a month and it always ends up the same. unless you have some major modifications to warrant the increase octane fuel it makes absolutely no difference, stop kidding yourselves to justify why you spent more then someone with the same car did at the gas pump.

06Pursuit

iTrader: (1)

Thats your opinion. Going strickly by the DIC and the km's remaining to tank i get way more millage with preimum in town then regular. Theres no ifs ands or buts about it. thats what the car says. im preaty sure these sensors are acurate so im gonna trust them for the most part (that oil life sometimes scares me lol) So again, if u wanna spend the buck go for it! I personaly use both because octane aside, preimium is a cleaner gas so it does help to runn it everyonce and a while. thats my 2 cents

cawpin

If they were tuned to run on regular gas it wouldn't make any difference going to a higher octane. Running regular 87 octane causes the engine to knock some and the computer retards the timing to compensate. Hence a power loss and crappy gas milage. Just because it runs on 87 doesn't mean it was tuned for it. The SS/SC will run on it too but it will be an even more noticable difference.

Paradox

Try 96 octane. I've been experimenting with different octanes in various weather conditions. 96 octane when it's about 65-70 gives me a very noticable boost in low end and mid range torque. I went as high as 100 octane when the temperature was in the mid 70's but noticed only a mild gain over 96 octane. My theory is that the tuning of the car / ECU is the limitation as someone previously posted.

Keep in mind my Cobalt SS/SC is still stock and anyone with mods such as a Stage II kit may get more out of 100 octane.

My friend had an EVO with 22lbs of boost and he uses C-16 race fuel at the track. He's currently running high 12's.

I have also noticed a difference between the lower cost octane boosters such as STP or NOS usually sold at the local parts store in the orange bottle, and NOS brand which sells for about $7-$12 at a local speed shop. I currently use NOS P/N 12002 STREET FORMULA which raises octane effect up to 3 octane points, not to be confused by the claims made by lower cost octane boosters which advertise up to 15 pt. boost and in small writing on the back of the bottle tell you that each 1pt = 0.1pt. of octane.

I have also found that using to much octane booster causes a loss in performance. At some point it's probably better to just use higher octane fuel. I going to make a bad anlogy to promote my theory.

THEORY: It's like adding a the ratio of water to coffee grounds that make the perfect cup of coffee... hmm... Okay, that's a bad analogy but I hope I've given some food for thought. Food... hmm...

rnjmur

Gas Myths and Answers:

1. Premium Gas burns cleaner - FALSE! Premium gas does not burn cleaner! On a car tuned to run 87 octane the gas burns LESS causing Catalytic converter and O2 sensor failure sooner. You also are helping to pollute our environment even more.

2. When I put Premium in my car I get better gas milage - FALSE! Since you are actually wasting 5% of your gas because it is not burning you are NOT getting better gas mileage. Just because the DIC says your gas mileage is higher does not mean it is so. What is probably happening is that the car "thinks" it is getting better gas mileage because it is trying to compensate for the fact it "thinks" it is running rich since the gas is not burning correctly.

3. During Spirited or Heavy driving the car responds better - TRUE! You may get a bit of a performance increase under heavy loads using premium gas because as the combustion chamber becomes increasing hot from hard driving the premium will allow the car to begin to burn the gas correctly thus eliminating having to retard timing due to knock.

Also as a side note - the DIC is not 100% accurate. If I drive a full tank of gas and stay out of boost the DIC is usually fairly close - within 1 MPG or so. However if I drive hard here or there or maybe burn a ricer or two during the week, the DIC has been off by as much as 5 MPG. So do not always go off the DIC for your true MPG.

You may want to try using 89 octane in your 2.2L balt. It will help reduce any knock you may get during city driving and will still continue to burn fairly effectively.

slowion2

lol

this is the only site I know of where someone's opinion is found true over fact. incredible.

rnjmur - if the ecu would advance timing then #3 would be true, but it's not very likely. you'd have to actually read your knock with both octane in the exact same variables. the theory is there and cars with a distributor can advance easily, but we cannot. otherwise you're right on point.

rnjmur

Notice I said on #3 it MAY help but I also put in there the stipulation that it only helps if it prevents the engine from retarding due to knock which can occur under heavy load/heat conditions.

To clarify - unless you are at the track doing multiple runs or at sustained high RPMs where the engine tempurature is high you will probably not see the performance gain of running premium in a car that only needs 87 octane. However the possibility of it having a slight performance increase is there so I can't really say that the myth is completely false even though it is only slightly true.

slowion2

hey I'm not saying you're wrong, I'm giving you praise for realizing this lol

but it's ok because we're both idiots hahahaha

06Pursuit

iTrader: (1)

all you guys tell us about octane and how the computer reacts....u all own SS/SC's!!! The 2.2 is not the same and reacts very diffrently then ur cars. Our computers don't have to compensate for boost and detonation because their made not too read any hense our whole turbo/supercharger delimma. Second of all, depending on where people live and the climate they drive in will also adversly affect the way the engine reacts to octane.

Brian MP5T

Sweet Jesus!

rnjmur

Hey I will admit idiocy pokes it head out sometimes... hehe...

And having a SC is what makes it necessary for our cars to run on premium gas - because the SC basically raises the compression level in the combustion chamber. Compression + Heat = need more octane or BOOM! detonation... and the 2.2L motors do have knock sensors so they can adjust timing.

All engine mechanics are the same whether you have a SC or don't have a SC. Yes climate can make a bit of difference but I don't think they were asking about the effects of octane at climate extremes.

Edit: All praise Sweet Baby Jesus!

D4u2s0t

you guys are idiots... octane is nothing more than gas's resistance to detonation... you are supposed to use the lowest octane that does not product knock... end of story.. nothing else... game over... end yourself...

using premium in a 2.2 is good for one thing, and one thing only... spending more money than you have to... you can trick yourself into believing that it's actually benefitting your car, but it's not... again, end of story...

people associate high octane with more horse power INCORRECTLY because higher horsepower engines call for higher octane... why?? do some research for yourself... i'm sick of covering the same topic over, and over, and over because some ricer thinks he's getting better gas mileage and 20 more hp from using 100 octane in his base model 126 whp car...

D4u2s0t

Game over:

importkiller

iTrader: (1)

my car runs smother on mid grade than regular but out here in CO regular is 85 octane.

marerick007

You might want to read the owner's manual. You must be getting some crappy gas for it to run bad on 87 octane, simply put. If it was tuned to a higher octane, then it would say it in the owners manual like the SS/SC recommends Premium.

marerick007

I also have a 2.2 LS Sedan as well. I know its not the same, AND I also know how it reacts. It boils down to the quality of the fuel you are getting if you have it run crappy on 87 octane.

marerick007

Thanks for the backup!

D4u2s0t

no prob

rally

The only thing that would matter for our gas is Top Tier Gas. Such as SHELL. It reduces the carbon build up over time and keeps the engine clean.

This Octane crap is just that, crap. Theres no way you can tell 100% that 90 octane gives you 5 more mpg. Its impossible because the driving conditions will never be the same or close enough on a city or highway to reproduce accurate results.

IonNinja

NGK 2 step colder plugs + 91 octane & my car feels like a Honda Civic

Brian MP5T

It has nothing to do with Economy...

It has to do with Detonation Threshold.

D4u2s0t

so you lost all your torque??

YSUsteven

ahhh.... this is the 2.2L fourm.

marerick007

Yeah, I noticed...thanks for pointing it out....

07BlackCobalt-LS

In the LS it is better on the engine to to run the lower octane gas. The compression in the engines doesnt burn the higher octane gasolines as well as the fuel milage thing is all in your imagination. I filled up regular reset MPG gauge and drove 20 miles. Average of 28mpg city. Next week filled up with premium cause it was only 2.11/g reset MPG gauge and drove the same 20 miles same speed and averaged 28 MPG. Same MPG on both gasolines and Regular gasoline in the LS and LT cobalts wont foul up the O2 sensor or spark plugs thats just plain bullshit that gas companys use to sell the higher price gas. It wont harm the engine using higher grade gas. But there is absolutly no difference measured by either a computer(stand alone fuel management) or on board MPG display if you actually drive completely the same both times in same style weather conditions, same acceleration, same everything. Please dont **** people up telling them that its gonna make a difference. Some people come here because they dont know the difference between the Alternator and the master cylinder and they will believe anything you tell them even if its wrong and just costing them more money.

Now if you have the SS or the SS/SC I would definitly reccomend using the premium. Price you pay for buying a forced induction engine. or High Compression VVTI engine in teh case of the 2.4SS