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, 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. Previously, EV mode went on up to 62 MPH. After the fix, EV mode could go up to something like 80 MPH. In theory, that would give highway drivers like me better gas mileage, if the engine could switch to EV at higher speeds. And it was indeed the case that I saw the engine occasionally switch to EV mode at the higher speeds, so that part worked.
However, after I accepted 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. 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 - the battery isn't as efficient in cold weather, you run the defrost and heat more, you let the car warm up, etc. So I couldn't really prove after that what was due to the Ford algorithm "fix" and what was due to the cold weather conditions. This has been a particularly cold, harsh winter, and now my overall gas mileage is down to 36.9 MPG (according to the car's computer).
I haven't tried the manual gas mileage calculations, partly because I think there are so many variables in that process. This Car and Driver article refers to them: how full do you fill your tank each time? how do you know how full it is when different gas pumps are calibrated to cut off with different amounts of back pressure? what about different manufacturers of fuel? differences between summer and winter fuel? heat and cold? The article suggested a particular approach to try to minimize some of the variables, but I'm not usually able to be that consistent, so I end up relying on the car's computer numbers.
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 they are limited in what they can do. I would like to hear from any other 2013 Ford Fusion Hybrid owners who have accepted the EV mode "fix" and to hear the experience of others gas mileage after that. 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.
