Feb. 21, 2008 - Honda is experimenting with a new hybrid engine that can recapture heat from combustion exhaust and convert it into electricity for the car's battery pack.

Current tests indicates the technology could bump fuel efficiency by 3.8% for hybrids driving at highway speeds. Honda says that it will likely wait until that percentage improves before putting the new engine into production.

For specifics on the new engine's design, read this article from Green Car Congress.