The 2009 Lincoln Navigator 4X2 now earns...drumroll...14 mpg city and 20 mpg highway. Respectable for the class, but significantly lower than both the Chevrolet Tahoe and Dodge Durango two-mode hybrids. Not to mention diesels like the Mercedes GL 320 BlueTEC (EPA 17/23 mpg). Clearly, Ford is trying to find a silver lining in its current situation, employing new transmissions and massaging existing engines while holding its breath for true engine breakthroughs still in the works.
Claiming the fractional improvements in mileage are due to "architectural changes and systems engineering enhancements," this latest announcement seems to be spawned primarily by "using aggressive deceleration fuel shut-off." Whenever you fully release the accelerator pedal in a modern car, the fuel injectors shut off to consume gasoline. But injector shutdown and startup must be done carefully to avoid being noticed by the driver as well as to avoid increased tailpipe emissions. Ford has increased the speed of this process, resulting in quicker injector shutoff and therefore less fuel used while coasting and braking. Cool, but a far cry from regenerative braking.
While it's great that Ford powertrain engineers are working on fuel economy subtleties such as these, we won't be truly excited until we see technologies that significantly increase fuel economy such as its upcoming EcoBoost engines (set to debut in the 2009 Lincoln MKS) and its upcoming medium-size turbodiesel V-8 for light trucks and SUVs.--Colin Mathews