Longer carbon chains in the molecules (according to Wikipedia "... resulting in a mixture of carbon chains that typically contain between 8 and 21 carbon atoms per molecule" compared to pure octane which is 8 carbon atoms per molecule) means that a greater proportion of the exhaust is CO2.
Obama's motto: Green for thee but not for me.
What counts is joules per ton of CO2, not the relative portions of CO2 and H2O. H2O is a greenhouse gas, but it has a halflife in the atmosphere of about a week, CO2, about a century.
Combustion entails breaking C=C bonds and C=H bonds and creating O=C=O bonds and H=0=H bonds. There (it appears to me, anyway) to be an increase in entropy post combustion, which adds to the available energy. You have to add up the electronegativity of all the pre - and post - combustion products, plus a dollop of entropy, to get the joules per ton of CO2. Or you could just measure.
What counts is joules per ton of CO2, not the relative portions of CO2 and H2O. H2O is a greenhouse gas, but it has a halflife in the atmosphere of about a week, CO2, about a century.
Combustion entails breaking C=C bonds and C=H bonds and creating O=C=O bonds and H=0=H bonds. There (it appears to me, anyway) to be an increase in entropy post combustion, which adds to the available energy. You have to add up the electronegativity of all the pre - and post - combustion products, plus a dollop of entropy, to get the joules per ton of CO2. Or you could just measure.