Recently, there was a demand to find unconventional solutions for energy. Therefore, the investigations concerned to discover alternative fuel such as compressed natural gas, methanol, biodiesel, etc. In this study, a new alternative fuel in vehicle engines is evaluated and, the reduction of the emitted pollution as a result of using this fuel. In addition, the effect of biodiesel fuel (cottonseed oil) on the engine performance mounted in hybrid electric vehicle during variant road conditions is investigated. A simulation model that describes hybrid electric vehicle components with mathematical forms is built to determine the performance of the electric vehicle according to a driving cycle inner city. The results illustrate that using biodiesel as a fuel in hybrid electric vehicle contributes to reduce the environmental impact, hence enhance the fuel economy. © 2014 IEEE.