Articulated lorry drivers in the Uk - revs / gear question?

I drive a Mercedes Actros 2546 with semi-auto box ( paddle change ). When carrying / pulling some weight, particularly at max gvw ( payload of 28.2 ton ) my question is this ; from stationary ie accelerating and building-up speed, at how many revs should I change up to a higher gear ? Ive been told that max torque is produced at 1100 rpm and max power at 1600 rpm , so is it better to rev the engine higher thus generating max power or is it more effective to change up sooner , at lower revs, and let the torque do the work ? Im thinking in terms of optimizing fuel consumption. Cheers.