Page "Delta IV" Paragraph 4

An upgrade of the Delta IV Heavy, using the higher-performance RS-68A engine, was successfully flight tested in a launch on June 29, 2012.

This upgrade provides a roughly 13 % improvement in payload capability to GTO.

The new RS-68A is also planned to be used throughout the entire Delta IV family, where at 106 % thrust it will provide a roughly 7 – 11 % improvement in GTO payload ( although this higher power level may require structural changes ; running the engine at the current 102 % produces a smaller improvement but requires less modification ).