If it is an automatic transmission...then leave it to the tranny computer to do
the shifting and follow the manual on OD or not (recommendation is really
a way to say if you don't follow their recommendation...then warranty
will/might be denied...yes, know out of warranty, but the comment still
applies...as the owner will be paying instead of the OEM)
If it is a manual, then the discussion on which gear to use is in context and learn
what your ICE's torque/HP curve looks like and chose the range on that curve to
be in while towing/cruising/climbing/etc
Anyone have the torque/HP curve for the OP's ICE?