Stewart Development's new EngineChek is a patented engine-monitoring device that is placed n your oil filter prior to installation. The special hi-glow stainless steel EngineChek screen fits inside the filter gasket and is positioned to trap any foreign material before it can disappear into your filter. Black carbon particles signify excess blow-by or poor crankcase ventilation. Tiny metal filings ca indicate bearing, camshaft or lifter water.