A method for feeding reducing agent or reducing agent precursor into exhaust systems of mobile internal combustion engines and an exhaust system are preferably used for internal combustion engines with high nitrogen oxide compound emissions. A feed time is established. An exhaust parameter and/or necessary quantity of reducing agent is determined and a feed state of the reducing agent is defined. The reducing agent is treated if the feed state does not correspond to a stored state. The reducing agent feed to the exhaust system takes place last. The steps are repeated multiple times. This permits reducing agent to be fed into an exhaust system in a state suitable for the exhaust temperature, so that complete conversion of reducing agent takes place and selectively catalytic reduction is also ensured. This reduces the quantity of electrical energy necessary for converting reducing agent. A motor vehicle having the system is also provided.