Someone asked for the relative energies of natural gas compared to
 Gasoline. What I've been able to gather is :
 1 cu/ft NG=1028 BTU
 1 gal Gasoline=125000 BTU
 C. Smith

Those are "sit and burn" BTUs.

In actuality, the efficiency of gasoline as a motor fuel is very low,
while the efficiency of natural gas is very high.  Otherwise, a NG or
propane-fueled car would have pretty much no range or power.  There are
gas-powered Crown Vics in service as police cruisers!

Gasoline must be stable as a liquid, then rapidly broken down and
vaporized before it will burn, so most of a gallon of gas provides no
power.  Natural gas must simply be heated, and a far higher percentage
burns.

Keith W

Well there is still the high BTU per cubic foot of gasoline.
The tank needed for NG is also big and heavy.

Paul Lamar



17.5 µg (0.000000039 lb) of antimatter gives 100W at 100% efficiency
http://en.wikipedia.org/wiki/Heat_of_combustion

(Anyone want to invest in my antimatter fuel company?)

This is a nice chart:
http://en.wikipedia.org/wiki/Fuel_efficiency#Energy_content_of_fuel

But, I noticed a little disclaimer, "Neither the gross heat of
combustion nor the net heat of combustion gives the theoretical amount
of mechanical energy (work) that can be obtained from the reaction.
(This is given by the change in Gibbs free energy, and is around 45.7
MJ/kg for gasoline.) The actual amount of mechanical work obtained
from fuel (the inverse of the specific fuel consumption) depends on
the engine. A figure of 17.6 MJ/kg is possible with a gasoline engine,
and 19.1 MJ/kg for a diesel engine. See specific fuel consumption for
more information."

http://en.wikipedia.org/wiki/Specific_fuel_consumption