Researchers have investigated reactivity-controlled compression ignition (RCCI) combustion in the past several years because of its excellent combustion, performance, and emission features. In this experimental study, the RCCI combustion strategy was investigated using mineral diesel/butanol fuel-pair at various premixed ratios (rp) on an energy basis (rp = 0.25, 0.50, and 0.75) at varying engine loads (BMEP = 1, 2, 3, and 4 bars) vis-à-vis baseline compression ignition (CI) combustion (rp = 0.0) strategy. Experiments were performed at constant engine speed (1500 rpm) in a single-cylinder research engine equipped with state-of-the-art features. The outcome of the investigation showed that port injection of Butanol as low reactivity fuel (LRF) improved the combustion and yielded superior engine performance than baseline CI combustion strategy. Engine exhaust emissions exhibited significantly lower nitrogen (NOx) oxides with butanol RCCI combustion strategy than baseline CI combustion strategy. Increasing rp of butanol showed improved combustion and emission characteristics; however, performance characteristics were not affected significantly. Particulate characteristics of the RCCI combustion strategy also showed a significant reduction in particle number concentration than baseline CI combustion. Slightly different combustion, performance, and emission characteristics of mineral diesel/ butanol-fueled RCCI combustion strategy compared to other test fuels such as mineral diesel/methanol, and mineral diesel/ethanol-fueled RCCI combustion strategy was an interesting observation of this study. Overall, this study indicated that butanol could be used as LRF in RCCI combustion engines to achieve superior combustion and emission characteristics.