Chevrolet has announced the Volt will carry EPA combined ratings of 93 MPGe (in electric-only mode) and 37 MPG (in range-extended mode).
(http://imgs.blackfalconmedia.com/2010/11/25/medium/199386999663374422.jpg)
Chevrolet Volt gets 60 MPG EPA rating (http://feeds.worldcarfans.com/~r/worldcarfans/Jxfz/~3/PzEdwwGv4ik/chevrolet-volt-gets-60-mpg-epa-rating)