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<misc> unleaded petrol

Shawn wrote (and quote from me):
>>The RON number is an indication of the fuels resistance to
>>knocking and detonation, it does not reveal anything about
>>the amount of energy in a given volume of fuel.
>>
>Actually it does. But surprisingly the LOWER the RON number more
>(stored) energy in a given volume of fuel. Unfortunatly if that
>energy is released before you want it to be (knocking/preignition)
>it is not of much use.

Now I quote from 2 places in your reference
(http://ram.chem.tulane.edu:8080/f-body/trivia/gasoline.html)

>The antiknock ability is related to the "autoignition temperature" of the
>hydrocarbons. Antiknock ability is _not_ substantially related to:-
>
>    1.The energy content of fuel, this should be obvious, as oxygenates have
> lower energy contents, but high octanes.
>    2. ...

and

> 4.13 What is a typical composition?
>
> There seems to be a perception that all gasolines of one octane grade are
> chemically similar, and thus general rules can be promulgated about "energy
> content ","flame speed", "combustion temperature" etc. etc.. Nothing is
> further from the truth. The behavior of manufactured gasolines in octane

Both of which I would say support my original statement - that the octane
rating cannot be used as a predictor of energy content (which your reference
places as between 42 and 44 MJ/kg Nett.)

BTW.  I love your reference, a very interesting page with lots of cool info.

Thanks,

Brendon.
'96 M3
'93 MX-5