The term 'GAP PLUGS, ETC.' is a reference to the automotive maintenance procedure known as a tune-up. A tune-up typically involves replacing spark plugs, wires, and other components that can become worn over time, as well as adjusting the air-fuel mixture and timing of the engine. This helps to ensure that the engine runs efficiently and reliably. The 6-letter crossword solution for this term is 'TUNEUP'.