The certification of the rheological properties of standard reference material SRM 2490, a non-Newtonian fluid consisting of polyisobutylene dissolved in 2,6,10,14-tetramethylpentadecane, is described. The viscosity and the first normal stress difference were measured in steady shear at rates between 0.001 s-1 and 100 s- 1 at 0 C, 25 C and 50 C. The linear viscoelastic storage modulus G' and loss modulus G'' were also measured in dynamic oscillatory measurements between 0.04 rad/s and 100 rad/s in the temperature range between 0 C and 50 C and master curves calculated using time temperature superposition.