The invention relates to a method for improving the efficiency of an SCR system of an exhaust gas aftertreatment system (5) of an internal combustion engine (1), and to an internal combustion engine (1), wherein an operating medium is metered in upstream of the SCR catalytic converter (2) of the SCR system in a normal operating mode, wherein the operating medium comprises a reducing agent or can be converted into a reducing agent, wherein the reducing agent is stored at least temporarily in an SCR catalytic converter (2) of the SCR system, wherein the method comprises the following steps: operating of the internal combustion engine (1) in the normal operating mode, defining of a determined control value (6) by way of determining of the mass of an exhaust gas component which is measured overall at a point in the course of the exhaust gas aftertreatment system (5) during a first measurement window, determining of a calculated control value (7) by way of calculating of the mass of the exhaust gas component which occurs overall at the point in the course of the exhaust gas aftertreatment system (5) during the first measurement window, determining of the deviation (8) between the determined control value and the calculated control value, checking whether the determined deviation lies within a predefined deviation range, adapting of the metering quantity of the operating medium if the determined deviation lies outside the deviation range.