A motor vehicle includes a tank for storing a liquid reducing agent suppliable to the exhaust system of an internal-combustion engine, and an air delivery device, by which an excess pressure can be built-up in a cushion of air situated in the tank above the reducing agent level. Via the air delivery device, alternatively, a vacuum is generatable in the air cushion, which vacuum supports feeding of the agent into the tank. Via the vacuum in the air cushion, reducing agent can also be returned from a pipe, which leads the reducing agent to the exhaust system, back into the tank, and/or additional liquid reducing agent can be transferred from a storage tank by way of a supply duct.