DH8-400:
at FL250 (max. certified FL) and max. cruise power approx. 1250 lbs/h/engine; TAS around 350kts.
DH8-300, same conditions: around 570 lbs/h/engine ; TAS approx. 240kts. It is worth noting however that on the -300 the maximum cruise power was reduced by up to 5% torque to keep the ITT below 700°c for engine lifetime reasons; this made TAS and fuel flow vary obviously. Also, due to the rather slow speed of this craft, it was sometimes necessary to stay around FL180 to keep out of strong headwinds and have a chance to keep the schedule; this of course resulted in an increased fuel flow as well.