The main source of power for Toyota's hybrids remains the gasoline engine. But these aren't your ordinary powertrains. They're built for high efficiency and low emissions. The Prius and Camry hybrids work off a four-cylinder, high expansion ratio Atkinson cycle engine.

Toyota has developed a new hybrid system for 2.0-liter engines, which applies the same size-reducing, weight-reducing, and loss-reducing technologies used in the fourth-generation Prius. The new system realizes improved driving performance while retaining superior fuel efficiency.