DannoMcK

A dying low-voltage battery is known to the Prius community to cause a drop in gas mileage until replaced. (I just traded a 2006 Prius for a 2016 FFH Titanium. Hi!) I presume that the hybrid system wastes energy constantly trying to charge a battery that is worn out and ultimately won't charge. It wouldn't surprise me that the Fusion Hybrid is subject to the same thing, but it seems like something the dealer would know about.