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["Don Bowen" <don.bowen AT earthlink.net>]

Some interesting information from
http://www.eere.energy.gov/afdc/pdfs/fueltable.pdf

BTU and stoichametric ratings
Gasoline    116090    14.7
Diesel        129050    14.7
Methanol    57250    6.45
Ethanol        76330    9.00
Propane        84500    15.7
Natural gas.    19800    17.2

I forgot to add one more important piece of information.  Stoichametric 
ratio or the Fuel / Air ratio.  For spark ignition engines, this ratio is 
when you have enough oxygen molecules to create complete combustion of the 
fuel molecules.  If you have more oxygen that fuel it is a lean condition, 
more fuel than oxygen is a rich condition.  Running rich means wasted 
unburnt fuel.  Running lean leads to more misfires and again wasted fuel. 
As you can see from above both ethanol and methanol require significantly 
more fuel per charge of air.

The small extra BTUs in Diesel are not entirely why Diesel gets better 
mileage.  Higher compression ratios, lower pumping losses, and controlled 
injection under stoich ratios gets more of the available BTUs out.
Don Bowen      KI6DIU
http://www.braingarage.com/Dons/Travels/journal/Journal.html