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This paper presents research evaluating the effectiveness of rejuvenators for production of very high (40% to 100%) reclaimed asphalt pavement (RAP) content mixtures. Nine differently originated softening agents were tested; these included plant oils, waste-derived oils, engineered products, and traditional and nontraditional refinery base oils. Two different dosages of the agents were added to binder extracted from RAP to evaluate their softening potential through testing of kinematic viscosity and penetration at two different temperatures. At 25°C the softening efficiency varied by a factor of 12 between the most and least effective rejuvenators. Consistency results at different temperatures were used to express temperature susceptibility by means of penetration index (PI), penetration–viscosity number, and bitumen test data chart of the softened binders. The PI results varied measurably depending on the rejuvenator and supported the low-temperature mixture test results, showing that PI may be a good and simple measure of rejuvenation effectiveness. Low-temperature mixture embrittlement was evaluated at 210°C through determination of the indirect tensile strength and creep compliance for rejuvenated 100% RAP mixture samples. It can be concluded that four of the nine tested rejuvenators reduced extracted binder consistency to the necessary level and reduced susceptibility of RAP mixtures to low-temperature embrittlement. Of the four, two engineered products tested had notably different performance but neither was superior to similar generic oils.