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Re: [Mgs] Reality, was:Oil Article

To: "Paul Root" <>
Subject: Re: [Mgs] Reality, was:Oil Article
From: "Paul Hunt" <>
Date: Fri, 16 Jan 2009 08:52:58 -0000
Not directly, but because it resists pinking better you can run with more
advance, and that *does* give better performance.  And if you don't use the
performance it gives better mileage.  More advance means more of the burn
occurs higher up in the down-stroke and it is that that gives the additional
power and economy.

There are occasional questions in uninformed motoring press here in the UK as
to whether it is worth paying extra for super unleaded over ordinary unleaded.
The answer is almost always 'no', which is probably correct, because the
people doing the asking have modern bread-and-butter cars with ECUs with fixed
maps that can only be changed by rechipping, even with knock sensing, which is
just used as an emergency timing back-off if knocking is detected.
Performance cars often use knock sensing to vary the map as well, and in those
cars you do get an improvement in performance, and my ZS 180 falls in to that
category as does my sons BMW M3 coupe.  Of course we can change our timing at
will, which is why our cars also benefit from higher octane.

  ----- Original Message -----

  Higher octane doesn't equate to more power. Higher octane resists
  igniting more. So you need
  more pressure (compression) to get it to fire efficiently.  This can
  generally correlate to poorer gas milage.
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