Large automakers are sitting out the Progressive Automotive X Prize competition for the time being, despite the green marketing opportunity.
No big auto companies are competing for the privately funded $10 million prize.
The X Prize money will be awarded in 2010 to a team that develops a vehicle getting at least 100 mpg that wins a series of races designed to simulate real-world driving conditions.
Vehicles that don't use gasoline must get the energy equivalent of 100 mpg.
Tesla Motors Inc. entered an electric vehicle in the mainstream category, which covers vehicles that meet strict performance rules. India's Tata Motors has entered an electric car in the alternative category, which has looser standards.
Other entries came from startup companies such as Aptera Motors, of Vista, Calif.; universities and high schools; and even the world of rock 'n' roll.
Neil Young entered a 1959 Lincoln Continental retrofitted to run as an electric vehicle.
Ten teams are from outside the United States.
Vehicles have to be "production capable," meaning they meet requirements for safety, cost, features and other criteria.
They also must be designed to sell at least 10,000 units a year.
Thirty-two entrants are electric vehicles, 23 run on gasoline, and 36 are hybrids using either gasoline or diesel engines. The rest run on a range of fuels, ranging from solar power to compressed natural gas.
Partly because the X Prize was unable to attract larger auto companies, the organizers established a "demonstration" division early this year. It gives major car companies a way to show off fuel-efficient technologies without committing the resources needed to develop a high-volume production vehicle.
X Prize spokeswoman Carrie Fox said organizers are talking with several major automakers about entering cars in the new division.