Chevrolet officials are touting the fuel efficiency benefits of its soon-to-be released Volt, but EPA is struggling with how to determine the vehicle's fuel economy, according to motortrend.com, a popular blog. The agency's struggle to certify the car's fuel economy -- which is needed for manufacturer issued window stickers -- comes from the novelty of the vehicle itself. The Volt, which Chevrolet intends to put on sale in 2010, is an electric car or a gas-electric hybrid ...or both depending...