Future vehicles will have many features that include, but are not limited to, drive-by-wire, telematics, pre-crash warning, highway guidance and traffic alert systems. From time to time the vehicles will need to have their software modules updated for various reasons, such as to introduce new features in vehicles, the need to change the navigation map, the need to fine tune various features of the vehicles, etc. A remote software update has a number of advantages, such as it does not require consumers to take their vehicles to the dealers, and the dealers do not need to spend time on vehicles on an individual basis. Thus, remote software updates can save consumers' valuable time, as well as cost savings for the vehicle manufacturers.Since wireless links have limited bandwidth, uploading software in thousands of vehicles in a cost-effective and timely manner is a challenge. Another major issue related to the remote software update is the security of the update process. In another paper, we addressed the security issue of the update process. In this paper, we present a wireless multicasting technique for uploading software in vehicles. Since the servers that will be broadcasting the software are located in some permanent places, and the vehicles are located all over the country, the software upload process has to depend on an infrastructure such as the cellular infrastructure. We have developed simulation models to determine the performance of our proposed wireless multicasting technique for remote software uploads. We simulated hundreds of vehicles distributed around a city area. In the simulation model, we assumed realistic speeds for the vehicles depending upon where the vehicles were located. The vehicles transfer the software from a buffer to an electronic control unit (ECU) when their ignition is off. Our simulation results show that if the multicast technique is used instead of the unicast technique (one vehicle at a time), then the software can be updated in a very cost-effective manner. The paper will give a detailed description of our technique and provide numerous results of the simulations collected for various distributions of the systems and vehicles.