[Steely Tom]

What has a higher energy density than diesel? Acetylene? Kind of expensive, not to mention unstable.

No ex-wife/girlfriend jokes please.

[thackney]

What has a higher energy density than diesel? Acetylene?

I think that would be limited to longer chain hydrocarbons. #6 Fuel Oil (bunker fuel) will have a greater energy density.

http://www.engineeringtoolbox.com/energy-content-d_868.html