Gas still has way more btu per gallon which is a lot more energy density.
Propane is one of the lowest with only 92,000 btu per gallon. Gas is
123,000 btu per gallon. Octane only helps you run a higher compression
which you could argue lets you make better use of the fuel. But in that,
diesel can run pretty high compression and it is the one fuel with even more
btu per gallon than gas, 138,000 btu per gallon.

"Richard Casady" wrote in message
...
On Thu, 2 Oct 2008 09:49:23 -0700 (PDT), wrote:

It's tough to beat the btu in a gallon of gas.

With propane the simplist, cheapest mixing valve will work as well as
the best fuel injection. Stuff is 100 octane, as well.
The stuff _is_ available many places. Slightly more BTU per pound
due to the slightly higher proportion of hydrogen. I had propane heat
at my previous address, and adding a fitting or two and a hose to the
1 000 gallon tank would have been easy. If I had had a 100 octane hot
rod I would have done it. Gas does have higher energy density but that
may not necessarily matter. It does with planes, more so than cars and
boats.

Casady