Use the oil dipstick to place 1-2 drops of engine oil in the center of the qualitative filter paper. Place the filter paper with oil drops on a flat surface, ensuring the back of the paper does not touch any object to avoid affecting the oil diffusion. Let it stand at room temperature for 0.5-1 hour, then observe the spot pattern. Additional information: 1. The purpose of the filter paper spot test method is to determine the clean dispersing performance of lubricating oil containing detergent-dispersant by observing its diffusion into spots on the filter paper. 2. The standard categorizes spot patterns into four grades. (1) Grade 1: The deposit ring and diffusion ring of the oil spot have no clear boundary; the entire spot is uniform in color, with a light and bright oil ring, indicating good oil quality. (2) Grade 1-2: The deposit ring of the oil spot is dark in color, the diffusion ring is relatively wide, and there is a clear boundary between the two rings. The oil ring appears in varying shades of yellow, indicating the oil is prone to contamination. Oil filtration should be enhanced, but the lubricating oil can still be used. (3) Grade 2-3: The deposit ring is dark black with dense deposits, the diffusion ring is narrow, and the oil ring darkens, indicating the oil quality has deteriorated. (4) Grade 3-4: The oil spot only has a central deposit ring and an oil ring, with no diffusion ring. The deposit ring is pitch black and thick, not drying easily.
