I have my proportioning valve apart at the moment, and I can see some rather nasty signs of wear occuring. Seems at the factory they put lithium grease in a few places but it wasn't looking to keen, sorta yellowed and pasty. The wear is specially noticable on the piston assemblies. So being of the idea that when it looks like it's wearing from moving and contacting the metal around it. But I'm not sure what greases get along with brake fluid or if I should just trust, caliper grease up in here. That's where I get a little leary beacuse the proportioning valve never gets hot and caliper grease tends to seperate. So I then looked at my Amsoil waterproof stuff, and my low temp ep grease, but I don't want the grease to turn abrasive either. So... What do I do?