Home › Forums › Stay Dirty Lounge › General Discussion › Copper Sludge? 6G72 3.0L › Copper Sludge? 6G72 3.0L February 3, 2020 at 12:58 am #895977 PaulParticipant The restore product contains particles copper, lead, and silver to fill the voids caused by wear, which may explain the flakes.