One thing I am NOT happy about is the lack of consistency of the Gas Mileage. I drive a route almost free of traffic. I use the dynamic cruise control at the same speed and I track outside temperature. I see a 5 - 7 MPG fluctuation in mileage over the 23 mile one way trip with the same outside temperature.
The are several factors that can affect your gas mileage over the same journey repeated. Although the car has a very low drag coefficient, it is at by wind speeds and direction relative to forward motion. Don't suppose you get lots of rain, but wet roads also increase fuel consumption.
Running the heater is the number one reason the motor runs in cold temperatures. Road and wind too but in cold weather the rolling resistance increases created by all the drag from cold mechanical components. I have only had my 2016 four for a month but am impressed at the gas mileage it gets in cold weather. My old 2008 would have gotten 43 on a day like today with Temps in the low 20's but on a 50 mile drive I got 63. One thing that could affect your short term mileage is the state of charge of the hybrid battery, If it is charged when you start driving you may get better gas mileage. If the engine has to run to charge it back up , we'll you get the picture.
Delta T is the numeric difference. It is neither positive or negative. It is the number between two numbers. It's most useful to set a specification: Close the shutters when the Delta T is 20. So when the difference between the inside and the outside temperature is 20, open the shutters. So if the temp inside is 90 and the temp outside is 70, open 'em up. Also if the inside is 70 and the outside is 90, open 'em up, etc.
