The formula of a gaseous hydrocarbon which requires \( 6 \) times of its own volume of \( \mathrm{O}_2 \) for complete oxidation and produces \( 4 \) times its own volume of \( \mathrm{CO}_2 \) is \( \mathrm{C}_x \mathrm{H}_y \). The value of \( y \) is _________.
