1. Reasons for the failure of lubricant

(1) Effect of high temperature

①Working under a high temperature for a long period, lubricant will be oxidized and lose its effect and become black and thick.

②The corrosive matters will increase in the lubricant, like the acid matters formed when the engine is working.

③Matters such as carbon residue, greasy filth and paint film will increase.

(2) Impurities

Impurities are mainly from dusts in the air, metal particles, leakage (fuel oil, water, etc.), oxide of lubricant and matters generated in the combustion of fuels, etc.

(3) Failure of additives

Some lubricants will decline in performance due to the failure or using up of additives. For example, when the anti-wear agent is used up in the lubricant, the anti-abrasion performance will decline.

(4) Failure of viscosity index improver

It no longer has the effect of thickening due to the rupture of long molecular chain of its organic matters.

(5) Failure of base oil

Base oil is the carrier of additives. When base oil fails, the additives will no longer work.

2. Method to identify failure of engine oil

Though there are national standards for determining whether to replace the lubricant of engine, most car owners or servicemen mainly judge by the mileage/time of cars (prescribed by the manufacturer) and color and viscosity of lubricant. In fact, the above methods all have unreasonable areas. For example, if judged by color, new lubricant of some brands is black, and some lubricants might turn black when added with too much purification dispersant, while at this moment, the lubricant has not lost its effect, which might be misjudged by those without adequate experience. The relatively simple and effective way is to use a filter paper or an analyzer to judge whether the lubricant has lost its effect.