[Dutchquade]

To be more fuel economical have small wind turbines fitted in the grill of the car, and Change the drive shaft of the car in to a dynamo to charge the batteries. Use the batteries to drive through urban areas while on the motorway / highway you can use the a small combustion engine.

Reward: The first commercial car which is fitted with these options.

[dolfin99]

There are numerous ideas such as this within the forums. Search and see what you come up with.

[Jras]

Ditto