Last summer drained the coolant out of the radiator and ever since the cooling system seems to be using fluid especially noticable when i go on long trips at high rpms. The engine temp according to the instrument cluster is at 90C generally and fluctuates between 85C and 100C depending on how hard I work the motor. This week, did a fresh coolant, water pump and thermostat change. I tried to get as much coolant out as possible. The results are the same. The systems seems to be slowly using coolant. I notice nothing in the oil to indicate a bad head gasket. I see a little white smoke at startup sometimes however it goes away as soon as the car has warmed up and I notice no lack in power or performance. about 17sec from 0-62mph and new the car calls for 15sec I believe. Is it possible there is an air pocket in the system somewhere?? All ideas are greatly appreciated. Auto in question is 1991 350SDL