It is rare for an attempt towards optimization at the fleet-level when consideration is given to the sheer number of seemingly unpredictable interactions among vehicles and infrastructure in congested urban areas. To close the gap, we introduce a simulation based framework to explore the impact of speed synchronization on fuel economy improvement for fleets in traffic.The framework consists of traffic and vehicle modules. The traffic module is used to simulate driver behavior in urban traffic; and the vehicle module is employed to estimate fuel economy. Driving schedule is the linkage between these two modules. To explore the impact, a connected vehicle technology sharing vehicle speed information is used for better fuel economy of a fleet including six vehicles. In all scenarios analyzed, the leading vehicle operates under the EPA Urban Dynamometer Driving Schedule (UDDS), while the other five vehicles follow the leader consecutively. Every follower in the fleet was governed by a driver behavior model and their desired speeds may be adjusted according to received speed information of the leading vehicle.Fuel economy for fleets comprising either all conventional or all hybrid electric vehicles (HEVs) were analyzed. The results show that the shared information contributes to fuel economy improvement more than 4% for the conventional vehicle fleet and at least 7% for the HEV fleet. The simulated vehicle kinematics is also analyzed. Since the analyses show promising results, research of further improving fuel economy with connected vehicle technology under real traffic conditions is recommended.