Reactivity controlled compression ignition has been introduced to implement controllable, clean, and high thermal efficiency without undermining the advantages of premixed combustion. However, simultaneous auto-ignition introduced by reactivity controlled combustion challenges the combustion under higher load operations. This experimental study incorporates a dual phase heat release concept with the purpose of improving the performance of reactivity controlled compression ignition engine. Different ratios of ethanol/diethyl-ether blends (from 0% to 40% diethyl ether and 70% premixed ratio) were applied to a light duty diesel engine at various combustion timings and engine loads. The diesel fuel was directly injected into the combustion chamber while ethanol/diethyl-ether blends were injected in the intake port. Engine performance and exhaust emissions were compared between the baseline operation and high blend ratios. An addition of 40% diethyl ether in the ethanol approximately resulted in 14% increase of the indicated mean effective pressure and 33% reduction in maximum pressure rise rate. The high reactivity of diethyl ether enhanced the oxidation of the hydrocarbons and resulted in lower hydrocarbon emissions. The higher volatility and better overall fuel-air mixing improved the combustion and reduced particle emission. Stable combustion was expanded at high load operating conditions due to double-stage heat release enhancement.