In PMB practice, the most common plasticizers are aromatic process oils, naphthenic oils, and heavy vacuum distillates, sometimes also flux oils from refinery streams. Their main benefit is to reduce the viscosity of the base bitumen and improve polymer swelling, which shortens curing time and improves dispersion stability. Good plasticizers also enhance low-temperature flexibility and reduce the risk of phase separation during storage. The key is compatibility: the oil must have good solvency for both bitumen maltenes and the polymer, otherwise it can actually ???????? storage stability instead of improving it.