Cooler weather

Now that we have cooler weather in the northeast I've been noticing that the electric motor does not appear to come on as quickly or as often. I called the Ford dealer. The service guru said that whenever the heater is turned on, and it has been cool enough to use it and I have, then the gas engine is going to run and the motor will not. Hmmm. I decided to test this on the FusionH. Went for a run, electric switched over, I then hit the heater. . .still in electric. Continued in electric. What gives? OK, maybe I have to hit defrost, that will probably kick on the A/C, no way it will stay in electric with the A/C. Tried it and still the Fusion stayed in electric, didn't miss a beat didn't even seem to notice. So that doesn't seem to quite be it.

Has anyone else had this experience with gas mileage dropping now that the temps are lower?

The interesting thing is this, once I am out on the road for 10 minutes everything seems to be exactly the way it was in summer. The engine comes on and goes off very easily. I just did a 20 mile errand on suburban streets and returned home with a mileage of 59.8 (I was trying to get 60!). Which is still remarkable, nearly an increase of 50% over EPA. And I had traffic behind me frequently so I was keeping or exceeding the speed limit. Seems like I always have a BMW SUV in my mirror just 2 car lengths back and itching to get by for that rush trip to buy a head of lettuce.

Anyway, has anyone else experienced anything like this?