Shredded nut shells (grain size less than 100 pm) were added sep. in proportions in the range of 5-25% by vol. to non-Newtonian heating oil and aq. polyacrylamide soln. to obtain hydrophobic and hydrophilic suspensions, resp. RheoL properties of the suspensions and clean liqs. were detd. by using the rotational rheometer with coaxial cylinders in a shear rate range 1-437 s(-1). Exptl. detd. viscosity values of suspensions were compared with values calcd. in accordance with various empirical relationships typically used for suspensions. Errors of calcd. viscosities in comparison to viscosities obtained exptl. strongly depended on the solid phase content in the suspensions and polarity of the liq. The calcn. method should not be applied to detg. the viscosity of suspensions contg. more than 10% of porous grain with the ability to swell in a hydrophilic environment.