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Old 08-26-2004, 12:45 PM   #11
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Quote:
Originally Posted by Jim W
Any high compression or supercharged/turbocharged car needs 90-94 gasoline all the time. The car states that on the dash cluster and the gas cap area.

Predetonation is a bad thing!
Hehe I'll assume you meant detonation, as pre-ignition is a whole separate issue
From what I've learned these statements are half right half wrong. As luck would have it we are equipped with a knock sensor. This will pick up detonation and retard timing in the milliseconds. This happens that fast. If you put lower octane in you won't hurt your engine but you will lose some performance as the computer retards timing to combat knock. This problem will be bigger in higher mileage cars as the carbon buildup requires higher octane than when the engine was new so you'll lose that much more power. This isn't harmful to your engine though so if you need to put lower octane in things should be fine. If you do experience a very harsh running engine and detonation its the knock sensor/PCM'* fault really.
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Old 08-26-2004, 07:36 PM   #12
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If you have adjustable timing, or you setup your BCS to dump boost lower, you can probably get away with lower octane. But premium will get you better milage in the SC cars.
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Old 08-26-2004, 08:42 PM   #13
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how bout 3/4 premium and 1/4 100 octane gas
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Old 08-26-2004, 08:44 PM   #14
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I don't know how the Y2K+ SSEi'* show, but my 1999 SSEi'* dash said "REGULAR UNLEADED FUEL ONLY". Only after you opened the fuel filler door did you see a sticker with red print stating "USE PREMIUM UNLEADED ONLY". In the owners manual it stated you could use 89 octane, but if pinging (detonation) or hesitating occured switch to premium immediately.
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Old 08-26-2004, 09:10 PM   #15
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Quote:
Originally Posted by OLBlueEyesBonne
I don't know how the Y2K+ SSEi'* show, but my 1999 SSEi'* dash said "REGULAR UNLEADED FUEL ONLY". Only after you opened the fuel filler door did you see a sticker with red print stating "USE PREMIUM UNLEADED ONLY". In the owners manual it stated you could use 89 octane, but if pinging (detonation) or hesitating occured switch to premium immediately.
Odd. My 93 clearly states Premium on the dash, gas door, and owners manual.
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Old 08-26-2004, 09:16 PM   #16
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Just incase anyone is new to this thread..... the rule is SCed engines need Premium, that'* octane 91 or higher.

“Hey, That smells like regular. She needs premium dude. Premium! DUDE!”
-Snake from the Simpsons
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Old 08-26-2004, 09:30 PM   #17
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Running anything other than premium in a supercharged car is bad even for a little bit. Lower octane gas does not burn as efficiently and can leave carbon buildup on the cylinder heads. Even a tiny bit of buildup can cause higher compression and even if you do go back to higher octane gas your tendancy to detonate will increase and your likelyhood of blowing a piston becomes higher.

Your flashing SES light is a heavy misfire code. I'm not sure bad gas would cause it, but you should check your plugs for fouling or a loose wire.
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Old 08-26-2004, 10:19 PM   #18
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Aww come on guys, I like a good debate! If you disagree with what I say please, pick it apart and show me which one you disagree with! haha Buuut lemme try this again:

The reason you may get better mileage with premium is because you'll lose power with lower octane fuel. The lower power requires you to press the gas pedal harder for you to get the same acceleration feel hence you burn more. This isn't the engine acting, its your foot.

The misconception about higher octane being cleaner is just that, a misconception. All octane ratings, no matter what the brand, contain cleaning detergents to protect against carbon buildup. This is actually mandated by the EPA.

If you want more info read: http://chemistry.about.com/cs/howthi.../aa070401a.htm

It gets complicated at times but its good info. So to quote me

DrJay says: "Using lower octane does not necessarily give you better gas mileage and is not bad for your supercharged engine. It also does not cause more carbon buildup. It is, however, bad for performance."

I wanna debate though
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Old 08-26-2004, 10:31 PM   #19
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I'm up for this debate, but mainly because I'd like to know. I was under the impression that carbon buildup would be more common, as well. Strange magic goes on in the cylinders when the engine is running. Hell, I've got a MESS of fouled plugs right now because of another crappy alternator, causing a weak spark. The RATE of ignition has an enormous effect on cylinder/plug cleanliness.

So let'* talk about what that higher octane provides. It ignites at a HIGHER temperature. This is of benefit to us with Blowers, as we don't PRE-detonate. Now the question is, does it burn quicker? If it burns quicker, we get a better burn, leaving less crud in the cylinders.

If it DOESN'T burn quicker, we may have just lost the argument.
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Old 08-26-2004, 11:05 PM   #20
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Lower octane will increase knock in boosted cars. Because the lower octane gas burns at lower temps the airfuel charge is ignited from more than one source (the plug) and the charge is not consumed cleanly and thus is less efficient. This leaves unburned fumes (as well as exhaust gas reinserted from egr which does have carbon) and will buildup over time. Add to this fact that most of our cars are boost stacking even from the factory and realize that air in the cylinder is not being ejected fast enough anyways you have more of a propensity for inefficent combustion.

Knock WILL hurt the engine and over time you will burn/chip/break a piston.
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