This paper demonstrates the improvement of a low temperature natural gas (LTNG) mechanism for simulating fuel ignition and combustion emissions under engine-like conditions. The LTNG mechanism was compared and validated in both the simplified zero-dimensional (0D)/one-dimensional (1D) reactors and three-dimensional (3D) engine models. In a 0D premixed constant volume reactor, the LTNG mechanism can more accurately predict the ignition delay than the well-developed GRI-3.0 natural gas mechanism, when the temperature is lower than 1300 K, compared to the experimental data. The results also indicate that the LTNG mechanism can well predict the formation of important carbon-containing gaseous species, such as acetylene and carbon dioxide, and nitrogen oxides emissions under typical engine conditions with and without technologies that implement low temperature combustion. In a 3D computational fluid dynamic model with a range of temperatures and pressures, the matched ignition delay curves from the numerical simulation and the experimental measurements indicate that the LTNG mechanism can improve the prediction of natural gas ignition and combustion compared to the GRI-3.0 mechanism. A further validation conducted in a direct-injection natural gas engine ignited by a hot surface illustrates the reliability of the LTNG mechanism for predicting natural gas ignition and combustion inside compression ignition engines. (C) 2019 The Combustion Institute. Published by Elsevier Inc. All rights reserved.