Just checked my records and I've put 13.35 gallons in. I never "try" to run out of fuel ... anymore. It's only happened twice to me a long, long time ago (not C-Max) when climbing longer steeper hills on the interstate. Also, IIRC, a few have run several miles (maybe 15 or so) after "zero miles to empty". I believe you can get near 14 gallons in the tank.
Fuel tank usable "rated" size (13.5 gallons in the C-Max Hybrid) is less than "fill up" size. There is a standard for tank size rating. For example, filler pipe, vapor air space at top of tank, fuel lines, low area at bottom where fuel pump usually sits and can't be reached by the pump are excluded from the volume calculation of rated tank capacity. In addition, if you fill the tank beyond the pump shut off, fuel can enter the EVAP system. Filling when not on flat ground, can result in fuel in the air space.
So, if you want to test the tank size, drive until you run out of gas making sure gas stations are near and where the ground is level as you will be able to drive in EV for likely 1/4 - 1/2 mile at low speeds once ICE stops running. Maybe you can set the fillup record!
Edited by Plus 3 Golfer, 17 November 2017 - 11:47 AM.