FLINT, Mich. — At a time when many people have put off buying a new car until the economy improves, the last thing we need is a stringent government regulation on fuel efficiency that will raise the cost of vehicles and make matters even more difficult for consumers. The Obama administration has mandated Corporate Average Fuel Economy standards that require automakers to make expensive redesigns on new vehicles. By 2016, the fuel efficiency of America’s new vehicle fleet will have to average at least 35.5 miles per gallon.