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2013 XTS
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Discussion Starter #1
I hear various speaches about 2000 being the year the northstar was redesigned to handle low octane gas. With that being said can someone tell me why when I put low octane gas in aka the cheap stuff I don't get the acceleration I do with the high octane ?
 

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I think it's all about the stuff itself .2000 and up also comes with lowered compression ratio .I will give you an example to makes things brigher for you ....In a Champ Car , if you use premium let alone regular stuff other than it's methanol fuel , the car will not able to go faster as it goes with the methanol .Same logic goes for your Seville as well .
 

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When I was in Chicago bringing my new STS home, I put some regular in it and got some pretty nasty missing. Next stop I threw premium in it and it was gone. I'm gonna start running 89 vs 87 from now on.
 

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Discussion Starter #5
I always thought it was the 93-97 Northstars that ran like crap if you put regular in them. I notice more power when i use 91 and the 89 here is mixed with ethanol and it dosn't seem to like that one bit because it really loses power then.
 

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I scanned my 1997 running 87 in it, and it was running 7 degress of knock. Emptied that tank, and ran 94 octane and ran 0 degress of knock, and a 0-60 time .7 seconds faster. lol
 

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The 2000 and newer Northstars run just fine on 87 octane and unlike the 93-99's will do so without retarding the timing, etc.

The 2000 engine was redesigned with a target of 300hp on 87 octane. They did this by improving the shape of the combustion chamber (which is now known to the be THE #1 issue on detonation) They reduced the compression ratio slightly and they improved the engines breathing with better roller cams etc.

I have run my 2002 on both (high test and low test) and every thing in between... 87, 89, 91, even 94...
In my car... No difference in performance, idle quality or milage.

My vote, Z06 hit the nail on the head:
Placebo effect
PS if the 89 has ethanol then the 91 has it too... maybe even more of it.
 

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White Diamond 2001 STS
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In the Northstar forum, statements were made confidently that even the 2000+ engines perform better on premium fuel. I know my '97 did, but thought that the '00+ engines were designed with the changes that Ur7x mentioned above, making premium fuel redundant in those engines. The suggestion was made that even on the 2000+ engines, premium fuel MAY offer more power and better fuel economy. I've always ran my '01 on regular, since that's what the owner's manual recommends. I do believe, however, that it does say that better performance could be acheived with the use of premium.

Who knows. I did fill the car with premium fuel this morning. It had less than 1/4 tank. I will run an honest 3-4 tanks of premium to see if I can tell a difference, either seat-of-the-pants or in fuel economy (my in-town economy is pretty regular, at about 18.5 or 19 MPG).
 

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Ya the owners manual says something like "for best performance use 91 octane"

On the mileage front... I did a long haul highway test on 87 vs 91 octane about a month a go... Drive down to Oregon I ran 87 Return trip two days later 91... mostly on Cruise control both ways usually set for around 72 MPH... The mileage was so close that I would call it a tie... (I actually got better mileage on the 87, which has always been my experience BTW).

If there is a difference I would bet in would be in the order of < 10hp... If GM could get 315 or 320 out of premium gas you bet they would have marketed that!

No out to start another "Octane debate" my observations are based on a statistical sample of one... Your car and your experiences will probably differ.
 

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Discussion Starter #11
I don't really care about the milleage i just care how fast my car is going to go when I mash the accelerator. I usually run the cheap stuff when the gas price gets to around 3.50
 

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A very cool and fair article!

As I suspected even in an over the top, hot rodded, 10.4:1, 395+ HP engine only made 6 extra horse power on premium.

Also of note... at the end of the article..
California pump gas is blended with methyl tertiary-butyl ether (MTBE), alcohol, and other ingredients damaging to performance.
This mirrors my West Coast experience... "High test" gas (in my 2002) means no change in mileage or performance.
 

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White Diamond 2001 STS
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I think there may be a difference between one specific engine developing "only" 6 additional horsepower at peak and the difference that premium fuel might make on a daily driver, in terms of driveability and mid-range throttle response. I can tell you that the difference between premium and regular was night-and-day in my '97. It may not have made any more peak HP on premium, but in the 2000-4000 RPM range, it felt like it had another 20. The throttle response was SO degraded on regular fuel, and it just didn't run "nice".

I have always complained about the lack of torque and low-end response from my '01 STS. Being the 300 hp engine, I knew there was going to be less torque. But I didn't think the difference was going to be so dramatic. But actually, after only a few days (57 miles to be exact) of running premium fuel in it, I can already tell a difference. I may not develop any additional horsepower @ 6000 RPM, but tooling around the neighborhood and city streets, I can tell a difference. Engine revs more effortlessly. It just seems to "breathe" better. This is exactly the difference I felt in my '97 -- regular fuel just seemed to "choke" it, at least in part-throttle situations.

I said I'd run an honest 3-4 tanks of premium before I made a decision, but I believe I already have. It was 104*F in town today, but the car ran like it was 70*F. Especially during this hot weather, the difference in octane HAS made a difference. It's not something a dyno would show. It's certainly not something my wife would notice (no offense to women, she just doesn't feel and hear the same things I do in a car). It's just something I can "feel".
 

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For what it's worth...

I just ran through my first tank of premium fuel (actually, about 80% premium, 20% regular). Unfortunately, I had been keeping tank-by-tank MPG records for only the three tanks prior, but my cost/mile was consistent (either 15 or 16 cents/mile). It's turned out that for the first tank of premium, I have broken exactly even in MPG gain and cost gain with the premium fuel. I was at exactly 15 cents/mile again this tank. I consider that a 'win', because I can feel as big of a difference in how this '01 runs as I did in the '97.
 

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I think it's all about the stuff itself .2000 and up also comes with lowered compression ratio .I will give you an example to makes things brigher for you ....In a Champ Car , if you use premium let alone regular stuff other than it's methanol fuel , the car will not able to go faster as it goes with the methanol .Same logic goes for your Seville as well .
You have been pump full of it. 00+ has how much less compression than a 99? .1 to .3? You can not run Methanol in a Northstar it is way to corrosive.

The 2000 and newer Northstars run just fine on 87 octane and unlike the 93-99's will do so without retarding the timing, etc.
The 2000 engine was redesigned with a target of 300hp on 87 octane. They did this by improving the shape of the combustion chamber (which is now known to the be THE #1 issue on detonation) They reduced the compression ratio slightly and they improved the engines breathing with better roller cams etc.

I have run my 2002 on both (high test and low test) and every thing in between... 87, 89, 91, even 94...
In my car... No difference in performance, idle quality or milage.

PS if the 89 has ethanol then the 91 has it too... maybe even more of it.
It is the same as a 99. I have looked at the Program in detail.
If you read the GM articles the 00+ needs 93 octane and must have it. It was tested with 93 octane to get the HP results. I have posted the GM info


A very cool and fair article!

As I suspected even in an over the top, hot rodded, 10.4:1, 395+ HP engine only made 6 extra horse power on premium.

Also of note... at the end of the article..


This mirrors my West Coast experience... "High test" gas (in my 2002) means no change in mileage or performance.
METB is not acceptable in ANY GM car or truck. It will cause sever damage

For what it's worth...

I just ran through my first tank of premium fuel (actually, about 80% premium, 20% regular). Unfortunately, I had been keeping tank-by-tank MPG records for only the three tanks prior, but my cost/mile was consistent (either 15 or 16 cents/mile). It's turned out that for the first tank of premium, I have broken exactly even in MPG gain and cost gain with the premium fuel. I was at exactly 15 cents/mile again this tank. I consider that a 'win', because I can feel as big of a difference in how this '01 runs as I did in the '97.
Jadcock TOPTIER is the magic word.
 

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I just got myself a Gtech thingy and I'm going to do some 1/4 mile runs on high test and on low test and I'll post the results... I'm not saying there isn't a difference... I'm just saying that my butt can't feel the difference.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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AJ, re: your last post, above regarding MTBE. Unless I am grossly mistaken, MTBE was the EPA gasoline emissions additive of preference until a couple of years ago, when the ethanol lobby convinced our elected officials (Read: election money) that MTBE was killing our children and grandparents. Every gasoline engine developed or designed from the mid-'70's to last year, whether built here or elsewhere and destined for U.S. use, was expected to run a MTBE based fuel. Your statement that "an MTBE based fuel will cause severe damage to a GM ......" is flat wrong. Actually, ethanol is far more corrosive and solvent than MTBE, but corn money won't tell you that. Look at what havoc the ethanol fuels have wreaked on the boating industry, and digest the fact that, right now, there's movement afoot to go to 20% ethanol and higher. The indisputable fact is that you MUST burn more ethanol per HP than today's petrofuels. (Top Tier generally refers to GM's fuel acceptance published specs and maybe if those fuels use Techron in their blend...)(The N* engine management system is smart...you run 93, the knock sensor circuits allow a smidge more ignition advance across the curve, and you get a slight performance boost. No brainer. Run 87, cheaper fuel/mile, knock sensor says "retard", and you drive to Florida at $.33 less per gallon than high test.)
 

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This is getting interesting. Ur7x please post back the results as I also can't feel the difference.
 
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