I know if you even get a small amount of brake fluid on the pads, the brake will tend to grab the rotor. Oil, on the other hand, does the opposite by allowing the rotor to slip. I used to have terrible brakes on my car. New pads all around made a vast improvement. I think the PO must have driven the car through a gushing oil well or something because all of the pads were oily and were equally poor at braking. Or mabe it had something to do with the once massive oil leaks that the car came with.