Chemical inhibition is one of the traditional methods used by the petroleum industry to prevent or correct the problems caused by the formation of organic deposits. In this work, three samples of poly(ethylene-co-vinyl acetate)s (EVAs) were added at different concentrations to three different Brazilian crude oils, and their effect on the wax appearance temperature (WAT) and crystallization enthalpy of the oils was evaluated as a function of increasing pressure and the type of saturation gas, using high-pressure microcalorimetry (HP mu DSC). The results show that different copolymer compositions present dissimilar performance in reducing WAT, and, in some cases, an optimum concentration was observed. When rising pressure, a positive influence on the WAT is observed, but the performance of organic deposition inhibitors that are ineffective at atmospheric pressure is not enhanced at higher pressures. On the other hand, additives able to modify the crystallization kinetics of waxes at atmospheric pressure show a synergy when evaluated in the presence of light fractions and under high pressures. HP mu DSC analysis is an important tool to optimize the additive concentration to be used in oil fields. (C) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012