To ensure engine gasket sealing, proper surface preparation must be performed, especially with the use of aluminum engine components and multi-layer steel cylinder head gaskets.Never use the following to clean gasket surfaces:Metal scraperAbrasive pad or paper to clean cylinder block and headHigh speed power tool with an abrasive pad or a wire brushMulti-Layer Steel (MLS) head gaskets require a scratch free sealing surface.Only use the following for cleaning gasket surfaces:Solvent or a commercially available gasket removerPlastic or wood scraper Drill motor with 3M Roloc™ Bristle Disc (white or yellow) Excessive pressure or high RPM (beyond the recommended speed), can damage the sealing surfaces. The mild (white, 120 grit) bristle disc is recommended. If necessary, the medium (yellow, 80 grit) bristle disc may be used on cast iron surfaces with care.