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Old 10-30-2007, 07:56 PM   #1
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Default Is premium gas necessary for a supercharged 3.8?

Just wondering. Perhaps mid-grade is ok?

Sorry if this question is asked all the time
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Old 10-30-2007, 08:01 PM   #2
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91 or better. Less for unavoidable short stints if you keep it easy on the throttle.
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Old 10-30-2007, 08:04 PM   #3
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yes, to keep form getting KR (knock Retard) you must run at least 91

The way i look at it, its only like another 2-3$ per fill up to run 93. so why not
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Old 10-30-2007, 08:05 PM   #4
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Old 10-30-2007, 08:12 PM   #5
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NOW I see the search button. Thanks all.
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Old 10-30-2007, 08:14 PM   #6
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There are 2 timing tables in the 96+ PCMs, one is designed for "bad gas" aka 85 or 87 octane.

On a stock car you can get away with it but if you are modded, dont even think about it.
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Old 10-30-2007, 11:05 PM   #7
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When KR is seen by the PCM, the knock has aleady happened.

It'* like scolding your dog to stop him from barking. The neighbors are still pissed.





In the case of KR, the damage happens slowly in small increments BEFORE the sensors and PCM see it. The bottom line is that if you are in a financial situation where you can't afford 91 or higher octane, you're better off selling the car. You will get more timing and higher mileage with the proper octane than you will with lesser octane, and you won't slowly kill your engine.
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Old 10-31-2007, 07:03 PM   #8
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If your close to stock as stated earlier the newer PCMs have 2 fuel tables. And there is a HUGE difference. I used to run 89 in my car thru the winter (it kept the car slow-er), granted it was cold so I was quite a bit safer. So for a temporary fix your fine, to do it permanently your slowly killing your car-very slowly! Just don't be a lead foot with low oct!

You can tell a huge difference in S2 L67'* that have been ran on low oct. most of their lives vs. one that has had higher oct. Go to the dealership and test drive one you'll see what I'm talking about.
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Old 10-31-2007, 10:50 PM   #9
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I run a L36 and i HAVE to run 93 to avoid KR, However, im running more timing, etc then most L36'* out there
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Old 11-01-2007, 12:33 AM   #10
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Perhaps I need to dumb it down again, lets assume for a second and take modifications out of the equation.

ANY vehicle that has high compression, or bolted on power adders like a supercharger or turbocharger will require high octane fuel to avoid pre-detonation. If you choose not to use at least 91 gas, the PCM will retard timing and you will experience poorer fuel economy and loss of performance.

You're car will still work, but its not worth the $$

Add in some mods that boost performance and you'd be a fool not to use the proper fuel.
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