The warmer the fuel the better for the thermal efficiency of the engine.Over this weekend I have been delayed on 2 "sleazy"flights and both times the Capt told diffrent(and more plausible)reason for the delays than the ground personel.The flight from EDI-STN this afternoon the ground staff said it was because of the French Civil Servants strike! and the Capt said it was because of an A/C problem when the A/C was in Luton.