I have a 2013 C-Max Hybrid SEL that I bought used about 9 months ago. No major issues so far. This week, I've noticed that after filling up the tank completely, the fuel gauge shows only 3/4 full. I know for certain based on the number of gallons I put in the tank that it is full. As I use the first quarter of fuel, the gauge will ping pong back and forth between 3/4 and the actual fuel level. After the first quarter, it seems dead accurate again.
Photo attached showing the gauge after a complete fill up.
Any ideas on what might be causing this or how to fix it? Provided it only affects the top quarter of the tank, it is just an annoyance, but if it starts affecting the rest, I may one day find myself running out of gas on the side of the road.