My 2015 sonic seems about that accurate as well(wtihin 1MPG most days), however i've had it as much as 6 MPG high if I'm at high RPM more than normal. My 2012 cruze always varied averaging 2-3mpg high so it nice to hear the new ones may be more accurate. I've noticed the 2014+ Silverado/Tahoe DIC calculated MPG is typically within 1MPG of actual as well so Gm must have changed something.Just filled the first tank on it. I left the dealer with a full tank and 16 miles on it. At 399.0 miles it took 10.616 gallons to pump shut off. So 383 miles, and 36.08 mpg. DIC average over lifetime is showing 35.9 mpg. So pretty close so far. That's probably 80% highway and 20% in town driving, roughly.
Thanks.All my tanks hand calculated are around 40-41 mpg. I am always about 50/50 city highway. The DIC is closer than any vehicle I've ever owned within 1-2 mpg. Today when I filled up it was about 0.2 mpg higher than calculated. Best 50 miles of 53.3 mpg on the DIC. I toy with it driving between hypermilling and spirited driving. I still think pure highway careful driving will be in the 50+ range. DIC over the last 3300 miles is 41.5. Average speed is 36.4 mph. It has been hot here and some time was spent idling filling out paperwork in the car. Sorry for the long post.