1. Observation
After cleaning, inspect the engine through the oil filler port. If there is no black sludge residue and the surface is metallic in color, this generally indicates a successful cleaning. For metal parts, wipe the surface with a clean white cloth. If there are no stains, it's clean.
2. Hydrophilicity Test
The cleaned metal surface should be completely hydrophilic. Immerse the workpiece in clean water and remove it. If a uniform water film forms on the surface with no oil spots or water droplets, the sludge has been removed. You can also use a Dyne pen test; if the line is straight and does not shrink, it indicates that the cleaning is satisfactory.
3. Filter Paper Test
Drop a small amount of cleaned engine oil onto white filter paper. If the oil ring is evenly spread, with clear edges and no impurities, the residue has been removed. If the center of the oil ring is dark or the edges are blurred, re-cleaning is necessary. 4. Red Ink Immersion Method
Apply red ink to the dry surface of the part. If a solid red mark appears after absorbing it with filter paper, degreasing is successful. If the filter paper shows areas without red, the oil stain has not been completely removed.
