Re: Octane vs. MPG

[Erik Lotspeich <erikvcl@xxxxxxxxxx>]

Michael,

There are a few issues here and it is important not to confuse them.  The
statement about higher octane containing more chemical energy IS correct.

1. Higher octane gasoline DOES contain more chemical energy.  This
is why jet fuel has higher octane.

2. Cars designed to use higher octane have higher-compression engines to
extract that energy.

3. Cars that are not designed for higher octane (e.g. lower compression
engines) will not be able to extract this energy and will perform more
poorly.

4. Using low octane gas in an engine designed for higher octane will
result in knocks and pings since pre-detonation will occur.

I hope that this clears things up.

Erik.


> Date: Thu, 19 Sep 2002 16:52:24 -0400
> From: "Michael Barrett" <mbarrett635@domain.elided>
> Subject: Re: Octane vs. MPG
>
> >Uh, to be clear, high octane gas render more energy. Ignition of a >highly
> >compressed air-gas mixture results in more energy than the >ignition of a
> >less compressed mixture.
>
> Uh, what's clear about your statement, other than it is incorrect?
>
> Octane enhancers are added to fuel to retard detonation -- ergo, less
> energy.  In the same engine, the higher the octane rating of the fuel, the
> fewer BTU's per unit volume of fuel.
>
> Octane does nothing to alter the compression of the air/fuel mixture, so I
> don't know what you're talking about there.

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