JANESVILLE, WI – The General Motors Assembly Plant in Janesville has produced its 500,000th flex-fuel vehicle, according to the Web site www.nbc15.madison.com. GM has been producing vehicles that run on regular fuel or E-85 ethanol since 2002. Flex-fuel vehicles will make up 70 percent of Janesville GM’s production this year. The state might reintroduce a “10 percent ethanol mandate bill” next session.