DAR Report post Posted August 28, 2020 (edited) I purchased my 2014 Ford Fusion SE Hybrid new in 2014. Never had a problem until this month. Had 99K miles on it and my 12 volt battery died. Trip to dealer where I purchased car. New battery plus I went ahead and did the 100K maintenance since it was in the shop. Now I am getting horrible mileage. I'm either 20 mpg or under or it goes to full electric. I used to be able to coast around town around 40 mpg per the display. Any idea what the problem could be? I had the coolant changed, new spark plug + 1 coil changed, and fuel injection service. So upset, car has 1 payment, and I love driving it with great mileage. Now I'm lucky if a get 30 mpg on a 10 mile trip (range before was anywhere from 45 - 60 mpg for same trip). Edited August 28, 2020 by DAR typos Quote Share this post Link to post Share on other sites
murphy Report post Posted August 28, 2020 They disconnected the 12 volt battery to install a new one. That means the computer lost all of its learned engine operating parameters. It will take a lot of varied driving for it to relearn the parameters. I forget what the mile number is. I think it is between 25 and 50 miles. Quote Share this post Link to post Share on other sites
DAR Report post Posted August 29, 2020 Since battery was replaced 3 weeks ago, I've driven over 500 miles (Road trip), and the bad mileage is continuing. Spent close to 1K on the maintenance, battery, and coil replacement. Quote Share this post Link to post Share on other sites
mwr Report post Posted August 29, 2020 1 hour ago, murphy said: They disconnected the 12 volt battery to install a new one. That means the computer lost all of its learned engine operating parameters. It will take a lot of varied driving for it to relearn the parameters. I forget what the mile number is. I think it is between 25 and 50 miles. It sounds like he already has at least those miles on the new battery. Mileage dropping from 45+ to 30 means to me that something is definitely wrong. Quote Share this post Link to post Share on other sites
Car man Report post Posted September 28, 2020 Hello, Have you checked your actual gas mileage with filling up your tank and using your trip meter? That could be much more accurate than the computer display.. If THAT mileage is also down significantly, then there is an issue. My advice, pay off the car and look for a replacement. Having driven Toyota's for 15 years now, I have been thinking about buying a Fusion hybrid as the Fusion is going out of production. Maybe I can score a deal, but the more I am reading about the Fusion, the more I am gearing towards the Camry hybrid. Quote Share this post Link to post Share on other sites
mwr Report post Posted September 28, 2020 1 hour ago, Car man said: I have been thinking about buying a Fusion hybrid as the Fusion is going out of production. Maybe I can score a deal, but the more I am reading about the Fusion, the more I am gearing towards the Camry hybrid. As a data point of one, I can only say that I bought my 2015 FFH almost 6 years and 80K miles ago and have had no problems at all. Gas mileage hasn't dropped at all, or anything else going wrong. Quote Share this post Link to post Share on other sites
jpohlman Report post Posted October 1, 2020 More than likely the transmissions learned customization dropped out of it. My experience is that when I reset it via IDS or Forscan it goes way down for a week, then I have to burn the next tank of gas down to 3/4 and then top it off with premium. After that my mileage is back up and I only use straight 87 octane. If all else fails have the dealer check the PCM for a calibration update. Quote Share this post Link to post Share on other sites
lolder Report post Posted October 1, 2020 Are you sure you're in "D" not "L"? Quote Share this post Link to post Share on other sites
Sky14FFH Report post Posted January 30, 2021 (edited) On 9/28/2020 at 3:15 PM, Car man said: My advice, pay off the car and look for a replacement. That's terrible advice. If this is happening right after service at a dealer, go back to the dealer and tell them they broke something and for them to make it right and do it soon. Brings us to the old dilemma "if it isn't broke, don't fix it". Hardly any "professional" can do their jobs right anymore and it's a real headache. But I'd get them right on it and don't wait any longer. If they don't then call Ford. Ford has been unhappy with the dealerships killing their business for a while now. I'm using a trickle charger now to keep my battery topped up in these cold temperatures but if it were to go I'd just do it myself since it is small and an easy unbolt rebolt. Edited January 30, 2021 by Sky14FFH Quote Share this post Link to post Share on other sites
