Comb-type (maleic acid alkylamides-co-a-octadecene) copolymers (MACs) assemble with long-chain n-paraffins and asphaltenes by the hydrophobic alkyl branches and polar groups, respectively, and improve flowability of crude oils upon cooling. Their effects on the crystallization of paraffins from model oils were studied by rheology, optical microscopy, differential scanning calorimetry, and X-ray diffraction. Upon cooling, MACs change the size and shape of paraffin crystals and reduce the yield stresses of gels generated by precipitated solids. Deposition of wax was significantly suppressed by MAC as observed using a laboratory-scale deposition apparatus. MACs are more effective than poly(ethylene-butene) copolymers in improving the flowability of crude oils containing asphaltenes. The interactions between the carboxyl and amide groups of MAC with the polar aromatic asphaltenes appear to stabilize crudes through the steric effects of the long alkyl groups of MAC polymers, thereby reducing the strength of paraffin/asphaltene gels formed on cooling. (C) 2011 American Institute of Chemical Engineers AIChE J, 2012