<div class="htmlview paragraph">MRV, CCS, and solution viscosity data were obtained on oil solutions of several OCP VI improvers with ethylene to propylene molar ratios of 60:40 to 80:20. High amounts of ethylene accompanied by some crystalline structure resulted in lower MRV and CCS values. For amorphous copolymers, intrinsic viscosities showed little variation with temperature over the range of −10 to 50 C. For partially crystalline copolymers they decreased precipitously at low temperature. The data can be explained by postulating that increased amounts of ethylene and resulting crystallinity lead to interaction and ordered domains in solution at low temperatures, giving rise to additional contraction of the copolymer above that expected for a totally amorphous material.</div>