Shear viscosity from Gauss-Bonnet gravity with a dilaton coupling

We calculate the shear viscosity of field theories with gravity duals of Gauss-Bonnet gravity with a nontrivial dilaton using anti-de Sitter/conformal field theory. We find that the dilaton field has a nontrivial contribution to the ratio of shear viscosity over entropy density, and, after imposing a causal constraint for the boundary field theory, the new lower bound 4/25π, obtained from pure Gauss-Bonnet gravity, may have a small violation.