Eco-routing is a technique proposed to optimize the fuel consumption in transportation networks. User feedback is used to compute the route's fuel consumption level for other vehicles to build their minimum path routes. When a vehicle traverses a road link, it reports its fuel consumption on this link to a Traffic Management Center (TMC), which updates the vehicles routing information and then vehicles are assigned routes based on this updated information. The vehicular network is responsible for transferring this information from vehicles to the TMC, where packets are subjected to delays and drops. To the best of our knowledge, none of the previous research efforts on eco-routing studied the effect of the data network and communication parameters on the performance of eco-routing algorithms. This paper, firstly, introduces a realistic simulation framework for eco-routing that can capture all the details of both the transportation and the communication networks. Secondly, it studies the effect of communication parameters on the eco-routing performance. The results show that the errors due to data packet drops and delay are not significant. Consequently, the algorithm is robust against drops and delay. However, the number and locations of the roadside units (RSUs) are important factors that affect the network-wide fuel consumption level.