Related link: http://www.nytimes.com/2005/04/02/business/02plug.html?pagewanted=all

NY Times: Hybrid-Car Tinkerers Scoff at No-Plug-In Rule - great story about Prius hackers getting huge gas mileage by plugging their cars into the electrical grid overnight:

Plug-in hybrid prototypes have been around for several years, but the idea of modifying a Prius stemmed from the curiosity of some Prius owners in the United States, Mr. Kramer said. They were aroused by a mysterious unmarked button on their Prius and discovered that in Priuses sold in Europe and Japan, the button allows the car to drive for a mile in electric-only mode. Mr. Hermance said the feature was disabled in Priuses sold in the United States because of complications it would have created in emissions-testing rules.

Mr. Kramer said “a bunch of engineers reverse-engineered it in the United States and figured out how to hack it.”