Use superunleaded or superdiesel, then you don't need any additional additives. After long ascents, after towing, after steady speed driving on a motorway, or after driving the car at high revs, leave it ticking over for around five minutes so the oil being pumped through the turbo bearings continues to lubricate the bearing instead of carbonising in the oil feed and oil return pipes. If the engine has stop/start and you stop on the motorway for fuel, etc, if the stop/start does not stop the engine, take that as a signal to leave it running for a minute or two. There's no need to idle the engine after stopping on short trips or low rev use in town traffic.