Temperature increase in vehicle cylinder during the fast filling process keeps arousing the interest of many researchers. In this paper a new fuel consisting of hydrogen enriched natural gas called "HCNG", and the influence of temperature distribution and elevation in HCNG tank were studied. A two-dimensional axisymmetric computational fluid dynamics (CFD) model for fast filling of HCNG vehicle cylinder of 150-L is established. The simulation is based on the standard k-epsilon turbulence model, and a real gas state equation is considered to evaluate the properties of the HCNG. The numerical simulations were performed with hydrogen mole fraction of 0%, 8%, 15% and 20%; the results show clearly the effect of the addition of hydrogen in methane. The increase in the concentration of Hydrogen is observed to be leading to a temperature increase. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.