As the importance of automotive electronics increases, the task of design and manufacturing becomes more difficult due to the growing number, size, and weight of the wiring harnesses. As an approach to resolve these problems, many multiplexing protocols such as Controller Area Network (CAN), Advanced PALMNET and J1850 have been developed by many automobile companies. In order to compare these protocols quantitatively, this paper presents the performance evaluation of CAN and Advanced PALMNET via discrete event simulation. Through numerous simulation experiments, several important quantitative performance factors such as the probability of a transmission failure, average system delay (data latency), and throughput have been evaluated. In addition to the performance comparison, the effect of data latency on a control system has been shown via simulation.