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Depending on where you are in the country sometimes even though it says you only need 87 because of impurities and altitude you need 89 for best operation. I sell and work on small engines and they specify a minimum 89 octane wheras most people buy the cheapest (87) for the lawn mower and wonder why it dies an early death.
 

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With having had 1 Bonneville SSEi, followed by 2 GTP's (with s/c) I can tell the difference between 87 and 93, although the onboard pcm and knock sensor will compensate for the 87 and just produce less power without (knock on wood) any apparent engine damage.
 

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brentil said:
Hmmm, I might just run 89 octane then. Eventually if GM offers a Supercharger/Turbocharger upgrade package I'll just be running 91+ anyways. :D
Speaking of F/I, I wonder what they are up to with the 2.0L Supercharged. I have started to see conflicting reports on the octane rating the engine needs. On the Ion, its 91. However, I have seen some written articles mention the Cobalt SS Supercharged runs on 87 Octane in their specs, and I have seen it numerous times. The Chevy US website does specify 91 too, but the Canadian site specifies 87! :willy: I suspect the 87 rating is wrong, but who knows? They have been tweeking the computer programing on the Ions for better operation. Maybe they are working on getting the engine to run well on regular fuel.
 

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Fformula88 said:
Speaking of F/I, I wonder what they are up to with the 2.0L Supercharged. I have started to see conflicting reports on the octane rating the engine needs. On the Ion, its 91. However, I have seen some written articles mention the Cobalt SS Supercharged runs on 87 Octane in their specs, and I have seen it numerous times. The Chevy US website does specify 91 too, but the Canadian site specifies 87! :willy: I suspect the 87 rating is wrong, but who knows? They have been tweeking the computer programing on the Ions for better operation. Maybe they are working on getting the engine to run well on regular fuel.
I'm betting it's supposed to be 91+ for all places. I personally would never want to run a forced induction engine on anyhting but 91+. You can do it on the lower octanes, but you're far more liekly to knock, and the power is greatly retarded a lot of times too to be able to do it.
 

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brentil said:
I'm betting it's supposed to be 91+ for all places. I personally would never want to run a forced induction engine on anyhting but 91+. You can do it on the lower octanes, but you're far more liekly to knock, and the power is greatly retarded a lot of times too to be able to do it.
I agree with you that it is highly irregular to run 87 in an F/I, and that I would be worried about knock killing the engine. However, if they could make one work fine on 87 without knock, it would be nice too from a money saving standpoint. At least as long as it didn't kill all the power from retarding the timing.
 

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Fformula88 said:
Speaking of F/I, I wonder what they are up to with the 2.0L Supercharged. I have started to see conflicting reports on the octane rating the engine needs. On the Ion, its 91. However, I have seen some written articles mention the Cobalt SS Supercharged runs on 87 Octane in their specs, and I have seen it numerous times. The Chevy US website does specify 91 too, but the Canadian site specifies 87! :willy: I suspect the 87 rating is wrong, but who knows? They have been tweeking the computer programing on the Ions for better operation. Maybe they are working on getting the engine to run well on regular fuel.
That is probably a markrting thing.
87 octane is around 80-82/liter ,91 octane is 90-92/litre( a dime more) which would be almost $0.40 more a US gallon. More people may buy car because it uses cheap 87 gas
 

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airbalancer said:
That is probably a markrting thing.
87 octane is around 80-82/liter ,91 octane is 90-92/litre( a dime more) which would be almost $0.40 more a US gallon. More people may buy car because it uses cheap 87 gas
I don't know about the new Miata, but the old one says it requires 91+ octane. I'm betting the new one wil too since it's taking the current 87 octane Mazda3 engine and increasing the HP.
 

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airbalancer said:
That is probably a markrting thing.
87 octane is around 80-82/liter ,91 octane is 90-92/litre( a dime more) which would be almost $0.40 more a US gallon. More people may buy car because it uses cheap 87 gas
The price difference in 87 to 93 Octane (stations around here don't sell 91, but have 93 instead) is almost always $0.20.
 

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Fformula88 said:
The price difference in 87 to 93 Octane (stations around here don't sell 91, but have 93 instead) is almost always $0.20.
If you think about it, it's not really that much more over the year (depending on how much you drive). If you fill up every two weeks, that's 26 times a year. At 13 galons IF you used every galon every time, you're paying an extra $2.60 per tank. That's a whopping $67.60 a year extra. It's not really that much if you think about it. Even if you filled up once a week that's still only $135.20 for the year extra.
 

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brentil said:
If you think about it, it's not really that much more over the year (depending on how much you drive). If you fill up every two weeks, that's 26 times a year. At 13 galons IF you used every galon every time, you're paying an extra $2.60 per tank. That's a whopping $67.60 a year extra. It's not really that much if you think about it. Even if you filled up once a week that's still only $135.20 for the year extra.
And if you had to have a fuel rail cleaning and throttle body decarbon done by the dealer because of more contaminants in lower octane you just saved a ton.
 

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There is nothing intrinsic about lower octane that says there will be more contaminants. If your low octane gas has contaminants, purchase your gas from a different vendor. A vendor who sells low octane with contaminants is just as likely to sell high octane with contaminants.

As a matter of fact, in an engine that doesn't get knock with either, you will get more power out of lower octane gas than a higher octane. Octane is a measure of knock inhibitors, which slow down the burn rate of gasoline. It is a myth that higher octane automatically equals higher horsepower. More explosive & faster burn = more power & more knock potential. Less explosive & slower burn = less power & less knock potential. You should always use the "optimal" fuel that an engine is designed for.
 

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SkyCaptain said:
There is nothing intrinsic about lower octane that says there will be more contaminants. If your low octane gas has contaminants, purchase your gas from a different vendor. A vendor who sells low octane with contaminants is just as likely to sell high octane with contaminants.

As a matter of fact, in an engine that doesn't get knock with either, you will get more power out of lower octane gas than a higher octane. Octane is a measure of knock inhibitors, which slow down the burn rate of gasoline. It is a myth that higher octane automatically equals higher horsepower. More explosive & faster burn = more power & more knock potential. Less explosive & slower burn = less power & less knock potential. You should always use the "optimal" fuel that an engine is designed for.
But then why do some companies like BP and Sunoco guarantee no fuel line freezeup and/or continual fuel line cleaning ONLY on their top octane fuels? They submit in their advertising that there is something different between the grades. Back in the days when you could actually change a fuel filter by yourself I had to change mine more often the more I used the lowest octane rated fuel. Isn't it true that octane requirement is also dependant on comp ratio. When the highest cp was 6/1 octane was in the 60's or 70's. What makes av gas different other than octane that you can't use anything else in the air?
 

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achieftain said:
But then why do some companies like BP and Sunoco guarantee no fuel line freezeup and/or continual fuel line cleaning ONLY on their top octane fuels? They submit in their advertising that there is something different between the grades. Back in the days when you could actually change a fuel filter by yourself I had to change mine more often the more I used the lowest octane rated fuel. Isn't it true that octane requirement is also dependant on comp ratio. When the highest cp was 6/1 octane was in the 60's or 70's. What makes av gas different other than octane that you can't use anything else in the air?
It's because they put addatives into their fuels specifically designed to clean your engine internals. That's what the Chevron with Techron is in essence, engine cleaner added to the gas. There's really nothing wrong with running lower octane. It's not going to clog up your engine and such. However dirty gas will.
 

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Yes, there are many additives to consider.

It's like hot dog sauce. No two are the same, and the amount of spices has no relation to the quantity of rat poop in your sauce.
 

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In the midwest, Quik-trip sells all their gasoline grades with a guarantee that if you have any fuel system related problems while using their gas-they will pay for the repair. Looks like they must put the same additives in their regular as they do in their mid-grade and premium.
 

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Octane

With 29 years in downstream R&D for a major oil company, maybe I can shed a little light on the octane discussion. Octane is simply a measure of the ability of a fuel to resist preignition detonation. We used to increase octane with tetraethyl lead, but now we control it by fuel composition only. For the chemists, that means more aromatics, olefins and isoparaffins. Generally the difference in composition has a minimal effect on energy content.

We put detergents and other additives into the gasoline to control deposits, etc. I feel pretty secure in stating that for any major brand, the additive levels are the same in all grades. The only difference is the composition.

One final thing, octane does cost! Most refineries are hard pressed to produce high octane gasoline. We run expensive units to produce high octane components (usually with a volume loss) from low octane components.

So if your car's knocking, or if the owner's manual says you need high octane, use it (as stated earlier, most cars that ask for high octane will "detune" themselves to use lower octane gasoline with some performance loss). You're not being nice to your auto by using gasoline with a higher octane rating than you need.

Okie Sol
 
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