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Discussion Starter · #1 ·
I have a 1999 Regal GS with the supercharger. I've been running it on premium lately just to not worry about it, but I used to run it on 87 or lower.

They say the problem with that is KR and knocking. But when I first got it, it was running regular fuel on a rusted muffler, undersized exhaust, gunked up cooling system, wide-open throttle during a heat wave, and my OBD reader's knock counter and KR readings had never budged.

Since then I got a large magnaflow muffler, did a triple flush of my cooling system, changed the thermostat, cleaned the MAF sensor, and changed the spark plugs. I've never experienced knocking or knock retard.

So how necessary is the better fuel? I feel like lower octane would burn more completely than higher when the pressure isn't as high, but that's just a hunch. Mainly, I'm interested in how this could mean sticking with premium, but getting a smaller supercharger pulley.

What are your thoughts?
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