AlpineRAM

There are 2 basic problems with the internal combustion engine-

A: To get good efficiency you need high compression, and high working pressure and temperature- but this increases the output of nitrous oxides.
B: Getting an engine to run efficiently over a broader spectrum of loads is extremely tricky and always a compromise.

So, basically if you take a modern car and assume the same weight of different powertrains the different models should have the same gas mileage. This is not so due to the points I stated above.
The ICE-Electrics combo makes a lot of sense if it's done with a rather small engine that delivers just enough power for sustained cruise at the desired speed, and electrics that give you the power to accelerate. (Especially since you can get your "fuel" back when braking, this gives you major savings in city stop and go)
Naturally it would be nice to do this with a highly efficient diesel- but in some cases the weight, the demand for space and the complexity of the exhaust treatment makes this a proposition that is actually less efficient than a gas engine.

Scotty

patdaly

The diesel/electric hybrid is the only way to go for those of us who don't live in urban paradises.

You wouldn't stand a chance out here in the real world, 20 miles from work in 20 below weather.............. It has taken me 2 hours to make it home, and nobody has a whiz bang battery to do that reliably just yet at least.