Board Thread:The Flash discussions/@comment-9346948-20160330001403/@comment-3423279-20160330140126

Chang Mou wrote: But Barry has never run to Mach 2 before. Umm.. he did so in order to go back in time during season 1 to try and save his mother.

Barry also recently hit Mach 3.3 in the Trajectory episode, even if he only did it briefly.