WAILUKU, HI --- Maui Mayor Charmaine Tavares is test-driving a Toyota Prius that's been converted into a plug-in hybrid as part of a study by Idaho National Laboratory and the U.S. Department of Energy. 

The car averaged 64 miles per gallon during April, the Associated Press reported. In other locations, the cars averaged between 44 and 59 miles per gallon. 

Tavares said she's spent nearly $87 driving 1,175 miles. That includes less than $47 for gas and $40 for electricity.