Dont wanna have a leak in your pants and be shot by an arrow in the same day. I live by this rule.
It sounds similar to that fluid used in suspension systems that flows like normal oil until a magnetic field is passed through it, then it suddenly turns incredibly viscous (almost solid, kinda like taffy. mmmm, taffy....). Cool stuff, but costs about $500/gal.
Plus upon hitting the pump the stuff would harden. Not fun for the impellor