Miata Mailing List: August 1993, Message #125
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   From: fischman@nynexst.com (Gary Fischman)
Subject: Re: Recommended octane
   Date: Tue, 17 Aug 1993 08:18:04 -0400



> Date: 	Tue, 17 Aug 1993 07:52:43 -0400
>
> Miata Floggers,
> Regarding the octane issue, I tried the 14 degree ignition advance trick
> and found that I needed premium or the car would knock under load at low
> revs.  I switched back and forth several times from Amoco premium to
> Amoco relgular.  Each tank of regular, it knocked; each tank premium it
> went away.  I haven't noticed any injector problems, and I'd hate to think
>  I'm causing some.
>
> BTW,this seems to
> be an odd effect (injector clogging) to expect from using premium.  Most
> name brand premiums now have additives that allegedly prevent this sort
> of thing.  In fact, BMW tests major brands of gas for exactly this purpose;
>  they had big problems with injector and intake valve deposits a while
> back.  It's a big thing for a gas to receive "BMW good valve-keeping award"
>  or whatever it's called.
> -Al
>
>

For the past 2 years (mine is 3 years old) I've *had* to run premium fuel
to avoid knocking at *high* revs.  The lower the octane, the more knocking.
With 93 octane, it seems to disappear entirely.
Basically, I'd get the knocking when doing a maximum accelleration beginning
at about 5000 rpm.  I haven't done anything with my timing (other than
replacing the belt).

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Gary J. Fischman		NYNEX Science & Technology Center
E-mail: fischman@nynexst.com	Wireless Communications Laboratory
Compuserve: 73750,2552		Room: 2C-10
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