Thanks a Lot.....the MKZ will get slightly worse fuel economy due to the additional weight and wider tires for sure. I was mainly concerned about the so called tweak for this..."The new software, Layden suggests, has the "engine speed harmonized with the [pedal] tip-in," producing a car that "feels connected, feels engaging, more like a driver's car." The engine response, he said, now feels "intuitive" to the driver"....this was posted on Greencarreports.com.