King Daniel Into Darkness wrote:
Yet whenever the Enterprise jumped to warp, the glow from the impulse engine faded first.
In the Kelvin's case, as far as I know, nothing suggests warp engines cannot be used for sub-light velocities.
We've seen this done both ways. In TMP, it's pretty clear that the warp engine is powering the ship as is accelerates from full impulse to warp one. In TWOK through STID we usually see the jump from a near standstill to warp speed. Sure, in TMP they were taking it slow with the new engines, but again the gap between full impulse and warp one is owned by warp drive.