Saturn L300 What type of engine coolant should I use for a Aug 18, 2011I recently got a check engine code P0128 on my 2003 L300 Saturn. The code states "Coolant Temperature Below Thermostat Regulation". I later replaced the Engine Coolant Temperature Sensor, but the engi read more How to Add Coolant: Saturn L300 (2000-2005) - 2005 Saturn Adding engine coolant (also known as antifreeze) to your 2005 Saturn L300 is pretty easy. Engine coolant circulates through your engine to keep it cool in the summer but won't freeze in the winter. Make sure to check your engine when it is cold for an accurate reading.