Critical Viscosity Exponent for Fluids: What Happend to the Higher Loops
  We arrange the loopwise perturbation theory for the critical viscosity exponent $x_{\eta}$, which happens to be very small, as a power series in $x_{\eta}$ itself and argue that the effect of loops beyond two is negligible. We claim that the critical viscosity exponent should be very closely approximated by $x_{\eta}=\frac{8}{15 \pi^2}(1+\frac{8}{3 \pi^2})\simeq 0.0685$. 
Palash Das and Jayanta K. Bhattacharjee