96 Fuel Question

I heard that the later C-4's had 2 different engine configurations that allowed for lower octane gas use. Does anyone know what VIN number is used
to identify which engine? Rob
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wrote:

Lt4's) but to my knowledge both required the same fuel. Bob G
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Bob G. wrote:

earlier C4s. The Electronic Spark Control (ESC) was supposed to handle the knock problem (sorta). I've tried both 87 and 89 octane in my '89 and don't like what I'd call "combustion roughness" (crappy timing) even at part throttle. I've used 87 octane in an '98 on long haul trips and found that the C5 adjusted much better (superior head design probably helped.) Dad has extolled the virtues of the C6 with reduced octane fuel. So, engines and fuels do get better as we forge ahead.
My LT1 & LT4 driving experience is very limited so I can't relate any experience with fuel in those cars. Both had better combustion chambers than did the aluminum headed L98s. Maybe someone has found that they do better with 87 or 89 octane than did the L98s. Just looking at the engine specs, I'd feel 'less uncomfortable' screwing around with 89 octane in an LT1 than in an LT4.
Hib Halverson has a discussion of fuel quality, octane, flame front travel and heads at << http://www.idavette.net/hib/fuel/index.htm . Although targeted at racing fuel, his discussion makes practical street sense to me. After Katrina, GW relaxed the wintertime environmental rules on West Coast gas. Calif refineries decreased the amount of oxy compounds in fuel and my C4 started sounding smoother and feeling quicker off the line. I didn't get the C5 until well after the Katrina changes so don't have personal experience with the LS1 engine and the new/old West Coast gas formulations. (And, I've only topped up the tank three times on this C5.)
--
…PJ
’89 HookerCar, ’02 E-blu 6-spd Coupe
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Thanks guys, I guess I can try a tank or two, but at 10 cents a gallon difference, that's only $2 or so on a full tank. It probably wouldn't make enough difference for the minimal cost difference. Rob

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