Not that I really know what I'm talking about...
I am under the impression that "bike grease stains" typically are hard to remove not on account of the grease, but because of the particles embedded in the grease, which flow into the fabric and stick there. Even if all of the grease is removed by solvents or detergents, the particles remain and the cloth remains stained. Once you've washed it once, you're screwed.
That said, this is about the best grease remover money can buy:
http://www.amazon.com/Clorox-Lestoil.../dp/B0002ZWAE2