A vehicle includes a fuel tank and an evaporative-emissions system having a primary subsystem and an auxiliary subsystem. The primary subsystem has a fuel-vapor canister in fluid communication with the fuel tank to capture fuel vapors of the fuel tank. The auxiliary subsystem is configured to capture fuel vapors associated with an external fuel-storage device. The auxiliary subsystem has an auxiliary port located on an exterior of the vehicle and is configured to connect with the external fuel-storage device. The auxiliary port is selectively connected in fluid communication with the fuel-vapor canister by a valve.