Hey Dram, look at it again, it wouldn't take a shot glass full to do that. Not trying to start an argument over a cylinder wall, but the stain area is only about 3/8-1/2" in the center tapering off to nothing on the sides making it no more than anout 3.5" long. A pint would cover the piston. Also if it's rock, it would be on the top on that side, not the bottom.