what about a diesel hybrid?

Yes, every diesel train is a diesel hybrid. Diesel hybrids can be very efficient.

There's a kit diesel hybrid car kit available, you might want to look at that.

Diesel would be a much wiser choice than the tradition gas/electric hybrids. Diesels run much more efficiently than gasoline, are more reliable, and more versatile (if you wanted to go really green and run bio-diesel, that motor is an excellent candidate for that as well). By all means, if you have the resources to do it, it would not surprise me if you saw 70-80mpg out of a system like that.

Good idea. Diesel engines are more efficient and produce less CO2. You may run into emissions problems in states like California, NY, and NH. Environmentalists in these states don't like diesels.

Diesel hybrids can be very efficient.. It was obviously nothing more than eye-candy at the auto show, but less exotic diesel-hybrid concepts continue to be dangled. The vision of a fuel-saving diesel-hybrid double whammy is too alluring for environmentalists to resist.