Experimental data are presented for the viscosity, pour point, and wax appearance temperature of a stabilized, waxy North Sea crude oil treated by 12 different commercial wax crystal modifiers, all of which may potentially act both as wax deposition inhibitors and pour point depressants. The viscosity data cover the temperature range from 40 to 5 degreesC. In general the studied chemicals only marginally influence the wax appearance temperatures whereas the majority has a pronounced effect on pour points and apparent viscosity. The viscosity data suggest that the inhibitors, probably by some kind of steric hindrance, "inactivate" wax components within a certain range of molecular weight by preventing them from building of network structures. It is shown that this effect can be modeled by assuming a lowering of the melting temperatures of the affected range of wax molecules.