I posted this under a different topic earlier, but I should have posted here. This is really good info that I look forward to using with my dealer.
I have a 2013 Ford Fusion Hybrid, and I generally love it. I never expected to get 47MPG - I think everyone knew that wasn't realistic.
From April 2013 until October 2013 (mine was built in March 2013), I was averaging around 39.x MPG overall (according to the car's computer). I commute 110 miles round trip, three days a week, or around 25K miles per year, mostly on the highway at 75 MPH. So I wasn't too unhappy with 39 overall. On some trips home from work (55 miles), I was getting 42 MPG when I drove conservatively on a slower-speed road. Then in October, I accepted the Ford PCM "fix" that changed the algorithm for when EV mode could kick in. After the fix, I saw the engine occasionally switch to EV mode at the higher speeds, so that part seemed to have worked.
However, soon after the PCM "fix", my overall gas mileage started to decrease. I have a very consistent driving route and conditions. Each time when I stopped the car, I looked at the mileage for that trip, and the numbers were lower than before the fix was applied. I could no longer get 42 even if I tried. This continued for the next 5 or 6 weeks. I mentioned it to the Ford dealer shop and they said to keep an eye on it. Well, after the weather started getting really cold in November and beyond, the mileage decreased even further, but that always happens with hybrids (and most cars) in the winter. So I couldn't really prove after that what was due to the Ford "fix" and what was due to the cold weather conditions. This has been a particularly cold, harsh winter in Indiana, and now my overall gas mileage is down to 36.9 MPG (according to the car's computer).
I am biding my time until warmer weather an more optimal driving conditions return. Then I plan to consistently measure my MPG again and see if it goes back up closer to what it was before the fix. I do plan to go back to the dealer and keep this issue in front of them. They seemed sympathetic, but now that I've learned more here, I plan to ask them to start over on the PCM fix. Is there something I can ask the dealer to specifically check again? They claim they have EV trained technicians and fixed it right, but I'm not a mechanic and can only press it so far on technical issues. Thanks for all the good info here.