I greatly enjoyed driving a small diesel while on vacation in the UK recently, but they are still too dirty for California - though strangely enough the big pickups and SUVs can run diesel engines because they're legally "trucks". The car got over 60mpg, though that was probably IMPERIAL gallons, not US gallons - be careful of units! Also, that was the car's own opinion of itself.
So, in California we're stuck with the Prius as the best current alternative, besides bicycles and feet.
OK, if the solar-powered racers can do better than 60mph in the race across Australia, there is interesting energy (and technology) here! In California almost all cars sit outside in the sun 360 days a year. No one uses garages here, either at home or at work. That sunshine is turning into heat anyway, either on the pavement, the roof paint, or heating the car. Using even 10% of it is a win. And there is a lot of interesting new solar technology coming on line - flexible panels, more efficient panels, and cheaper (less efficient) panels.
interesting fact about the Prius is that it has TWO batteries - one for starting the engine and normal automotive-electrical stuff, and the big battery pack for the hybrid stuff. I had to jump-start a friend's Prius after a party then the little battery was dead (lights left on?), while there was plenty of charge in the hybrid pack, which was somehow inaccessible. Here's an IT angle - the control software hasn't been debugged into all the corner cases yet!