WASHINGTON – Michigan’s senators and lawmakers supporting more fuel-efficient cars established a tenuous consensus Thursday that environmentalists complained could hurt California’s quest to tighten emissions, and hinder the EPA from regulating greenhouse gases in the future. Sens. Carl Levin and Debbie Stabenow, D-Mich., refused to vote for an energy bill to move forward unless Sen. Dianne Feinstein, D-Calif., agreed that the tough new fuel efficiency standards in the bill would not be undercut in the future by actions by the Environmental Protection Agency on global warming. Feinstein has been the chief proponent of fuel efficiency standards in the Senate, while Levin and Stabenow are the auto industry’s chief champions in the chamber. Since cars and trucks are a significant source of the carbon dioxide that causes global warming, any attempt to regulate greenhouse gas emissions could result in the need for even stricter fuel efficiency standards than the landmark 35mile-per-gallon fleetwide level in the bill that passed the Senate on Thursday evening. 160Want local news?Sign up for the Localist and stay informed Something went wrong. Please try again.subscribeCongratulations! You’re all set! AD Quality Auto 360p 720p 1080p Top articles1/5READ MOREWhicker: Clemson demonstrates that it’s tough to knock out the champAutomakers, who are currently developing new vehicles that won’t appear in showrooms for several years, have said they need certainty in the requirements and would face hardships if the requirements change. Before a key vote on the energy bill Thursday, Levin, Feinstein and Sen. Daniel Inouye, D-Hawaii, chairman of the Senate Commerce Committee, signed onto a so-called “colloquy” – a conversation among lawmakers that’s entered into the congressional record and can be used to determine congressional intent. In the colloquy, the three lawmakers specified that all federal regulations in the future would be consistent with the fuel efficiency standards in the bill. California wants to implement tailpipe emissions standards that would require the auto industry to build vehicles that produce 30 percent less greenhouse gas by 2016.