  We show that relativistic hydrodynamics in Minkowski space-time has intrinsic
ambiguity in second order viscosity parameters in the Landau-Lifshitz frame.
This stems from the possibility of improvements of energy-momentum tensor.
There exist at least two viscosity parameters which can be removed by using
this ambiguity in scale invariant hydrodynamics in (1+3) dimension, and
seemingly non-conformal hydrodynamic theories can be hiddenly conformal
invariant.
