what gas in my 65 GTO - Pontiac GTO Forum
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post #1 of 8 (permalink) Old 05-29-2017, 09:17 AM Thread Starter
 
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what gas in my 65 GTO

Hi all,
a lot of confusion here in France regarding this subject:
what kind of gas should I put in my 65 GTO 389CI V8?
currently I use unleaded 98 plus lead additive;
is that correct?
some guys here says they use 95 without additive;
so, where is the truth?
thanks for your feedback;

Eric
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post #2 of 8 (permalink) Old 05-29-2017, 07:33 PM
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Use the lowest octane you can without the engine pinging. Lead additive is not needed.
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post #3 of 8 (permalink) Old 05-30-2017, 03:54 AM Thread Starter
 
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hi, gtoguy,
the confusion comes from the fact that all the engines were designed in the 60's according to the leaded fuel used at that time;
the unleaded appears later in the 90's;
so the fact there is no more lead does not harm the valves?
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post #4 of 8 (permalink) Old 05-30-2017, 09:33 AM
 
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You have that backwards. Lead helps the valves to not wear themselves up into the head. Hardened valve seats were introduced when unleaded gas was becoming a reality. In 1973 it was mandated with the 1974 model year.
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post #5 of 8 (permalink) Old 05-31-2017, 09:05 AM
 
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I use 93 octane unleaded non ethanol with no additives on my 64 389 and it runs great with no pinging.
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post #6 of 8 (permalink) Old 05-31-2017, 09:15 AM Thread Starter
 
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happy to ear that!
so I 'll put 95 in it; (we don't have 93 in France !!)
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post #7 of 8 (permalink) Old 05-31-2017, 09:31 AM
 
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The United States uses the R+M divided by 2 method to advertise octane. Don't believe Europe uses that method, just Research Octane number. You really need to study & find out what "95" actually is, I'm betting it is much lower R+M divided by two.
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post #8 of 8 (permalink) Old 05-31-2017, 09:49 AM Thread Starter
 
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what stand for R+M?
I know that our 95 is actually 85 and our 98 is actually 87
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  Pontiac GTO Forum > The 1964-1974 Pontiac Tempest, Lemans & GTO > 1964-1974 Tempest, Lemans & GTO General Discussion

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