Equipped with just what the doctor, and the public, ordered, the Lincoln MKZ has a powerful and responsive 3.5-liter V6 good for 263 horsepower under its hood. Not as refined or gutsy sounding as some competitors’ engines, Lincoln’s new V6 nevertheless produces quick acceleration. Fuel economy could be better; we averaged 19 mpg during a week of mixed driving. The new six-speed automatic transmission sends power to all four of the MKZ’s wheels, shifts smoothly and responds dutifully, but needs a manual shift mode instead of a rudimentary overdrive-off button. Also, on more than one occasion during a rolling stop in traffic the transmission kicked down harshly when getting off the brake and onto the accelerator at speeds less than 10 mph.