This work seeks to confirm the possibility of using Dimethyl ether (DME) as an additive to the blend of pure Natural gas or Natural Gas/Hydrogen blend to improve performance, efficiency, and emissions of a homogeneous charge compression ignition (HCCI) engine. In the proposed technique, Hydrogen could help to extend the operating range of CNG fuel in HCCI engine and decrease the regulated emissions significantly, while DME will play a major role in controlling the auto-ignition timing of the HCCI engine combustion especially at low intake charge temperature. This task has been achieved herein theoretically and numerically with farther validation by the experimental work. The main goal was to find the optimal operating conditions of CNG HCCI engine with the minimum number of laboratory engine tests. In addition, we focused on configuring the HCCI engine to operate with natural gas as a main fuel within a range of values of the air/fuel ratio, engine parameter such as compression ratio, brake mean effective pressure, and fuel additives. Finally, we used all the controlled boundaries of the HCCI engine operating range that had been implemented to define misfire, ignition, and knocking limits as a baseline data for the calibration of the engine simulation programs.