Octane revisited

["Michael Barrett" <mbarrett635@xxxxxxxxxxx>]

>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.

I don't dispute #2-4, never have.  If you recall, the original question 
addressed getting more power by using higher octane.  As you correctly note, 
you need to use the octane level your engine requires; more is wasted, less 
is bad.

I continue to disagree with your statement regarding the fuel containing 
higher energy, particularly with regard to jet fuel.  JP-4 is essentially 
kerosene. Perhaps you are thinking of AVGAS, which is high octane gasoline, 
specifially intended for use in high compression piston powered aircraft, 
which correlates with your point #2.

Mike Barrett




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