wwhitney wrote:jlsoaz wrote: My understanding (and going from memory) is that a gallon of gasoline when combusted will release anything from (very roughly) under 100,000 btu to more than 130,000 btu.
Your comment got me curious so I decided to check wikipedia. The fuels commonly called gasoline produce between 111,000 and 115,000 BTUs/gallon, so the range is much tighter. But diesel produces 130,000 BTUs/gallon, while E85 produces only 82,000 BTU/gallon.
if we go by the link you provided, then I guess, but it is just one link. I suppose it is possibly correct that that the range in reality is tighter than the range of numbers I ran into when researching this years ago, but I think part of the problem is if I checked different sources I ran into different numbers and sometimes differing more widely than you have mentioned. If we take a quick check now we see also this:
Gasoline contains about 42.4 MJ/kg (120 MJ/US gal, 33.3 kWh/US gal, 120,000 BTU/US gal) quoting the lower heating value.  Gasoline blends differ, and therefore actual energy content varies according to the season and producer by up to 4% more or less than the average, according to the US EPA.
In my own calculations I eventually ended using something in the 33.x-34.x kWh per gallon range.
It has been too many years since my last chemistry class for me to have a handle on incorporating LHV and HHV understanding into the conversation, but the point was and is basically that when I went to look into these things, I found a range, and this brought home that the energy released when combusting a US gallon (or for that matter, a kilogram) of the fuel is not consistently the same across all gallons and this is logical I think because it is not just one set molecule but
"It consists mostly of organic compounds obtained by the fractional distillation of petroleum, enhanced with a variety of additives."
This is not to treat wikipedia as that reliable, but for purposes of a quick look at something.