Dale Smith wrote:

Which fuel has more energy, 110LL or 80/86 ?

Actually there may be no difference, or a slight one either way. Octane is a
measure of the "anti-knock" properties of a fuel.  A high power engine that
requires high octane has a higher compression ratio.  Burning high octane gas
in an engine that doesn't need it for anti-knock reasons is a waste of money.

Energy content per unit weight of fuel is a function of the carbon chain
length, i.e. kerosene > gasoline > butane > propane > methane.

Bill Schertz

I would vote for 80/86 (by a slight difference).  My understanding is pretty much
the same as yours ... lower down on that list is more BTU per liter of liquid (or
gas).

The octane additives (used to be tetraethyl lead ... in pre-EPA days) always raised
volatility, thus lowering the BTU available per unit of fuel.  If I recall it
allowed lower cost exhaust valves (and seats) also ... Detroit loved it.    Fill er
up with "Ethyl", soldier?

A bit ironic that millions of dollars have been wasted by motorists thinking that
high octane fuel would give them better performance or more effeciency, when in
fact, all they were doing was giving energy away (and paying more for the privledge
... ah, advertising).

Dale Smith

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