The best    Kerosene. Use a hard brush ( use a scissors to cut short a normal brush ) and brush hard on the chains, cassettes and chain rings. Can brush the FD and RD also. Then after 5 minutes, wash away with water and then use soapy water clean everything up. Been using it since I started, better than citrus degreaser or any degreaser for that matter. Just make sure the kerosene don't go into the disc brakes if you are using disc brakes.