Method and control unit for operating a spark-ignition internal combustion engine or a dual-fuel internal combustion engine operated in the spark-ignition mode

A control unit for operating an internal combustion engine, wherein the control unit is configured to:

• receive from a sensor a measurement value of a total base number and/or receive from a sensor a measurement value of an oxidation of a currently used lubricating oil in an oil circuit configured to lubricate the internal combustion engine;
• determine an exchange oil quantity based at least in part on the measurement value of the total base number and/or the measurement value of the oxidation;
• emit a first control signal, the first control signal configured to control a first valve, as a function of which the currently used lubricating oil is removable from the oil circuit to an extent corresponding to the determined exchange oil quantity is removable;
• and
• emit a second control signal, the second control signal configured to control a second valve, as a function of which new lubricating oil is suppliable to the oil circuit to an extent corresponding to the determined exchange oil quantity.