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Octane, high is not always better?

To: british-cars@encore.com
Subject: Octane, high is not always better?
From: Timothy Lyle Smith <tsmith@plains.NoDak.edu>
Date: Tue, 19 Feb 91 07:11:18 -0600
    On a recent trip I was having many prob;ems with my car, a 74 MGBGT.
It would sput and sputter if I drove slower than 75 mph even though it 
was warm, the carburators were warm, when their cold they don't work at
all.  Anyways, I put up with it for 200 at which time I had to fill up
again.  To conserve cash I filled with 87 octane rather than the 93 I
had used before.  To my surprise the car ran smoothly, no sput or sputter.

  Now I have been of the opinion that the higher the octane the better.  I
can not say that this is based on fact, just that for some reason I thought
that higher was better.  Now I'm thinking that if the octane is too high it
causes pre-ignition and lowers the gas mileage, first probably causing second.
In fact my mileage went from 20 mpg at 93 octane to 25 mpg with 89 octane.
Given the change in gas mileage I think that even when running at 75 mph on
the 93 octane gas it was still having problems even though it didn't sound
like it.

  Well oh saged ones, and other knowledgable folks, am I right?

  What is really stupid is I remember reading somewhere that the B only needs
91 octane.......


Tim


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