The liquid-liquid equilibria of water + n-decane, water + n-hexadecane, and water + methylcyclohexane have been measured separately with the two oxygenates 2-methoxy-2-methylbutane (tertiary amyl methyl ether or TAME) and 2-methyl-2-butanol (tertiary amyl alcohol or TAOH) at 25 degrees C. All of these systems exhibit type 2 liquid-liqud phase diagrams, though the shapes of the diagrams for the TAME and TAOH systems are quite different because of the much higher solubility of water in TAOH than TAME. One of the observations from our experimental data is that the addition of either TAME or TAOH to a hydrocarbon + water mixture results in an increased water solubility in the hydrocarbon phase and a decreased hydrocarbon solubility in the aqueous phase. This observation may be important when both the water pollution potential of possible gasoline reformulations and the sensitivity of the gasoline to water are assessed. We have found that the general features of the liquid-liquid phase diagrams can be accurately correlated with either the NRTL or UNIQUAC model, though some of the high dilution concentrations are incorrectly described. Finally, the liquid-liquid UNIFAC model leads to qualitatively correct predictions for the liquid-liquid equilibria of the systems studied.