What's the operating range of the MDS in the '09 and '10 5.7 V8, ie the vehicle speed? Also, what is the impact of the MDS on avg fuel economy shown on the trip computer during level cruising? I thought the MDS kicks in from 40-60mph and had a significant increase in fuel economy. However, my brother in law said it works up to 75mph on his Challenger R/T and the mpg increases by 2mpg to a spot average of 25mpg when cruising on the highway at 70mph. A 2mpg increase when MDS kicks in seems low considering that half the cylinders aren't in use.