I find turpentine (or similar stoddard solvent) to be a better solvent where "varnish" residue from gasoline has built up, though not needed for things like bike components. Back in the day, I used stoddard solvent in parts cleaners working on powered aircraft and motor vehicles.
Like many others, I just let particulates settle to the bottom of the jar and pour off the supernatant.
Benzene is particularly bad because of it's mutagenicity.