My manual says 16.2 US GAL.
I have filled up right at the 1/4 tank mark, and it took 12 gallons.
I have filled up at the 1/2 tank mark, and it took 8 gallons.
I have filled up at the 3/4 tank mark, and it took 4 gallons.
I wont fill up from empty.
lastly, the needle does go slightly above full, which would probably support the 16.2 gallon theory.
*Former Owner* of a 2006 DSM 2LT
*current owner* of a 2009 Victory Red SS