Increasing driving ranges of compressed natural gas (CNG) trucks is one solution to promote an alternative and green fuel. One major issue is that the trucks have short-driving ranges because the gas contains low physical density. However, due to a high hydrogen-to-carbon ratio in the gas, the CNG trucks emit cleaner emissions than gasoline/diesel-powered vehicles. To increase the driving range, a basic simulation study is performed on the effect of engine technologies on the fuel consumption of the concept CNG truck equipped with a parallel hybrid powertrain. The parallel hybrid light-duty delivery truck equipped with a production-typed engine is modeled using commercial software. Engine map data are taken from a modified spark-ignition engine with a compression ratio of 17 operated under variable valve timings (WT) and are used as inputs into the vehicle model. The effects of the WT engine on fuel consumption reduction are discussed. The results show that the average fuel consumption of the CNG truck equipped with the hybrid powertrain is improved by 15% relative to baseline data of the conventional powertrain under the JE05 driving cycle using a small-size hybridization.