U.S. motorists are getting a reprieve at the pump just as the shift to cheaper winter gasoline begins, with GasBuddy data showing the national average price falling 3.6 cents over the last week to $3.12 per gallon. Diesel also eased 2.6 cents to $3.658. The slide comes as refineries ramp up supply and seasonal regulations loosen, setting the stage for further declines. “While gas prices fell in more states than they rose last week, the West Coast continues to face challenges, with Oregon and Washington seeing some of the largest increases…