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Discussion Starter · #1 ·
My car is essentially stock (A code) and probably never had the heads off let alone changing anything to run on unleaded vs. regular gas. Should I run 94 octane (can get locally at Sunoco) or just tap water, er 87 octane ::? Any issues running unleaded (not that there's much choice :) )? Thanks.

Kelly
 

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As long as you don't get any "octane ping", sounds like chains dragging under the car under acceleration, I'd use the 87. There are lead sustitutes out there, I tried one, every time I used it, following the directions, I foul out my two plugs closest to the carburetor! Now I only use it about every other fill-up, and not quite as much as they reccomend. Do a search here on "lead substitute" and you'll see quite a few opinions on its' use!
 

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The octang rating is a number used to identify the antipinging of the fuel. for a standard engine you will gain nothing except a lighter wallet for using a higher octane fuel. If your car pings then you might need to move up to mid level fuel (assuming your care is properly tuned). The purpose of the tetra ethyl lead was to increas the octane level. It had a side benefit of impregnating the valves and valve seats to work like a lubricant. with unleaded fuel the valves can start wearing the valve seats. Modern heads and new valve jobs usually have hardened valve seats to prevent this from happening. SO if your car has orig heads, lead substitute might be suggested.
 

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Discussion Starter · #4 ·
Thanks for the feedback, guys. With the GN, I'm familiar with octane requirements (28 lbs of boost = 116 octane :: ). I'll look into lead substitute in the archives.

Kelly
 

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Even with original heads, many people will swear that a lead substitute is NOT necessary. I tend to agree with them...


Anyways, octane is a rating of how slowly the mixture burns, and if you're using a low octane (too low for your motor) you'll experience detonation because the fuel will be consumed too quickly in the combustion chamber.

My recommendation: Use 87 octane, go out on the highway, floor it, and if it doesn't "ping" then keep using 87. If it does "ping" then use that gasoline as fast as possible and step up to 89.

Pinging is synonymous with engine death. DO NOT let the engine "ping".
 

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Woah, another GN owner. ::

These cars aren't no where as finiky as GNs when it comes to octane. If you're really worried pour in some 93 and forgetabouit. :p

James
 

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Discussion Starter · #7 ·
Yup, C-16 is a little more expensive than good ole Sunoco 94 ::
 

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Anyways, octane is a rating of how slowly the mixture burns, and if you're using a low octane (too low for your motor) you'll experience detonation because the fuel will be consumed too quickly in the combustion chamber.
No, octane ratings describe the fuel's resistance to auto-ignition. The flame front speeds of pump gas doesn't vary significantly with octane rating.In fact, if some factor makes the mixture burn more slowly, knock/detonation/pinging will get WORSE, not better. Fast burns are a good thing... hence inducing swirl in the induction charge, or putting in dual plugs to get two flame fronts going, or MSD ignitions to get multiple flames going... a slower burning mixture runs counter to each of these mods.
 
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