Platooning has repeatedly been shown to have the potential to increase both the efficiency and the safety of future road traffic. Yet, while there is ample research that illustrates its potential in freeway scenarios, the biggest challenges of traffic efficiency and safety lie in urban environments, which pose unique challenges: They are characterized by the presence of tight speed limits, intersections, traffic lights, and buildings. Moreover, work that has targeted such scenarios has, so far, not considered platoon formation strategies - or only considered idealized vehicle dynamics, platooning controllers, or wireless network dynamics. We fill this gap by investigating dynamic platoon formation at urban intersections controlled by regular traffic lights. We propose a fuel-efficient strategy for platoon formation at such intersections and investigate its performance using realistic simulation models of (all of) vehicle dynamics, platooning controllers, and wireless networking. Our investigation reveals both challenges in wireless networking as well as the potential of the proposed strategy to simultaneously save both 15 \% of fuel and 14 \% of travel time.