In everyday life, when lubricating oil becomes degraded, it typically appears dark black, with abundant foam and has already shown emulsification. When rubbed between fingers, it lacks a thick consistency, feels gritty, or has an odor. Dropping it onto a white test paper results in a deep brown color, with no yellow stain area or many black spots. Failing to replace it promptly can accelerate the wear of parts, affect the engine's lifespan, and even lead to safety accidents. Today, we'll introduce the simple identification methods for lubricating oil quality.

Oil Flow Observation Method

Grab two measuring cups, one filled with the lubricant to be inspected and the other empty on the table. Lift the lubricant-filled cup 30-40 cm off the table and tilt it, allowing the lubricant to slowly flow into the empty cup. Observe its flow; quality lubricant should have a slender, even, and continuous flow.

Hand-rolled method

Rub the lubricant between the thumb and forefinger, repeatedly grinding it. A good lubricant feels slippery, with minimal particles and no friction. If you feel a noticeable gritty friction between your fingers, it indicates a high concentration of impurities in the lubricant. It should no longer be used and new lubricant should be replaced.

Photometric Method

On clear days, lift the lubricant test stick at a 45-degree angle to the horizontal surface. Compare the oil droplets against the sunlight and observe. Under the light, a clear absence of metal shavings in the lubricant indicates good condition and the oil can continue to be used. If there is an excessive amount of metal shavings, it is advisable to replace the oil.

Oil Drop Trailing Method

Grab a clean white filter paper, drop a few drops of lubricant on it, wait until the lubricant seeps through. If there is black powder on the surface and a gritty sensation upon touch, it indicates that there are many impurities in the lubricant. High-quality lubricant should be free of powder, feeling dry and smooth to the touch, and leaving a yellow stain.