The piece of your wardrobe that is closest to your body all day, every day, should fit comfortably and blend in without squeaking at every move. Although the squeaky wheel usually gets the grease, don't grease your underwire bra. Oils will deteriorate the synthetic fibres and can irritate your skin. Your bra squeaks because the fabric is too tight around the underwire. Give your bra a tune-up by making necessary adjustments for the perfect fit that will silence the squeak.
Remove your bra and lay it flat.
Straighten any cloth that is twisted around the underwire.
Straighten the underwire to a smooth "U" shape if it looks bent or distorted in any way.
Put your bra on and hook it on the usual hooks.
Check the position of the wire making sure there is enough width to go around the breast. Move the back hook of the bra to a larger size offering the wire more room to move.
Bras should be hung to air dry and stored laying flat in a drawer.
Do not tumble dry bras. Heat drying breaks down the elastic and fibres and shrinks fabric. Tight fabric around the underwire is the underlying cause of squeaky bras. If your underwire digs in, your cup size is too small.