Multifunctional isocyanurates are tailored as new additives for improving POM melt flow (“High Speed POM”). In a versatile one-pot synthesis, reacting trimerized hexamethylene diisocyanate with various alcohols and amines, functionalities, branching, and n-alkyl chain length are readily varied. The influence of substitution patterns on POM rheology is investigated. Adding 3 wt% isocyanurate urethane (I3O) together with 0.33 wt% nanosilica increases POM melt flow path by 60%. Large POM stacking boxes are molded at temperatures lowered by 40 K. This markedly enhances cooling and reduces cycle times. Isocyanurate urea (I3N) does not require nanosilica addition. Lubrication mechanisms and the role of in situ gradient formation, as measured by AFM, are studied.