On 07/20/2017 10:59 AM, Ed Pawlowski wrote:
Clark says the gauge is "dead nuts accurate" €” if you consider all the
variables at work during driving, including temperature, driving
conditions and driving style. The biggest fluctuation occurs because
ethanol, which is blended with gasoline in varying amounts, contains
less energy.

We have mandated ethanol blended gasoline in the winter months. It's
good for a couple of mpgs. That's in early November before warming the
car up in below zero weather and running the heater full tilt happens.
That causes another drop.