well, both steam and internal combustion engines lose a lot of energy as heat, vibration, and noise.
IIRC, the best ICE efficiency is about 10% throughput or conversion of chemical energy into torque.
steam engines have a crippling weight-to-horsepower ratio.
the problems with both systems are great,
solveng them in combination will be tricky, if even possible.
one notion: capture heat and vibration through thermo-electric and piezo-electric means and convert it to electricity for use in running electric wheel-hub motors?
Now we're communicating! Regenerative braking systems almost cry out for electric wheel hub motors, (and generators!)
I would add electrical energy capture from the shock absorbtion system.
The typical engine would capture explosion energy by pushing a magnetic field through a coil. This would come from a "cylinder" which was ideally designed for the dual purpose of developing expansion from combustion and steam vaporization.
Such a "car" might tend to look like a rolling lab bench, but I think the possible efficiencies would be demonstrable.
"solveng"???
DARKA!