The fastest the Enterprise in ST:TNG ever went was Warp 9.65 during "Q-Who"- though the ship was still accelerating and probably ended up in the Warp 9.8 range.
In "All Good Things", the three engined Enterprise-D was apparently capable of Warp 13 as that is the speed Admiral Riker ordered after the battle with the Klingons.
So presumably that was quite fast.
But.
The U.S.S Pasteur was capable of Warp 13 as well. Captain Crusher ordered that speed when leaving for the area near the anomaly.
And the Pasteur didn't look like it was a real speed burner.
So how fast could the Enterprise-D go in all likelihood?
In "All Good Things", the three engined Enterprise-D was apparently capable of Warp 13 as that is the speed Admiral Riker ordered after the battle with the Klingons.
So presumably that was quite fast.
But.
The U.S.S Pasteur was capable of Warp 13 as well. Captain Crusher ordered that speed when leaving for the area near the anomaly.
And the Pasteur didn't look like it was a real speed burner.
So how fast could the Enterprise-D go in all likelihood?