The source of Shuimei can't be determined, because it is definitely not a regular imported commodity. The regular imported commodity must have a Chinese label with the logo of China Commodity Inspection on it. However, the seller of Shuimei claims that Shuimei was imported into China through the customs through regular channels, that is, the seller denies that it was smuggled, so it can be judged that Shuimei is a fake.

most of the parallel imports are fakes, and the water beauty mentioned is really not covered with plastic film, so the general lack of power, increased noise and obvious engine jitter indicate that the oil needs to be replaced. The performance is not bad, but the noise is a bit loud, which is a fatal version for a commercial vehicle. The noise directly affects the rest of customers, so the GT Maroon 5 oil with excellent noise reduction ability was replaced.

the selection of engine oil should be based on the requirements of the engine. it is not necessary to use too high-grade engine oil on the engine with lower requirements, nor can lower-grade engine oil be used on the engine with higher requirements. multi-grade oil should be selected as far as possible.

Multi-grade oil has a good protective effect on the engine because of its economy, long service life and high efficiency. Based on the characteristics of multi-grade oil, the phenomenon of premature blackening and lower oil pressure may occur during use, which are all normal.

Extended information:

The engine is the heart of the car, and there are many metal surfaces in the engine that move against each other. These parts move fast and have poor environment, and the working temperature can reach 4°C to 6 C.

under such harsh working conditions, only qualified lubricating oil can reduce the wear of engine parts and prolong the service life. So what requirements should qualified lubricating oil meet?

that is to say, what are the seven functions of lubricating oil?

lubrication: there is rapid relative sliding between the piston and the cylinder, and between the spindle and the bearing bush. To prevent the parts from being worn too quickly, it is necessary to establish an oil film between the two sliding surfaces.

there is an oil film with sufficient thickness to separate the surfaces of relatively sliding parts, so as to achieve the purpose of reducing wear.

auxiliary cooling: because the specific heat value of engine oil is low, and it is inside the engine, it does not have cooling effect.

However, the engine generates heat energy due to fuel combustion. When the engine is working, the engine oil can bring the heat back to the oil tank and then radiate it into the air to help the water tank cool the engine. The real cooling effect is the water (or antifreeze) outside the engine shell.

Cleaning: Good engine oil can bring the carbides, sludge and worn metal particles on the engine parts back to the oil tank through circulation, and through the flow of lubricating oil, the dirt generated on the working surface of the parts is washed.

sealing and leakage prevention: the engine oil can form a sealing ring between the piston ring and the piston, so as to reduce gas leakage and prevent external pollutants from entering.

rust and corrosion prevention: lubricating oil can be adsorbed on the surface of parts to prevent water, air, acidic substances and harmful gases from contacting with parts.

shock absorption and buffering: when the pressure at the engine cylinder mouth rises sharply, the load on the piston, piston chip, connecting rod and crankshaft bearing suddenly increases, and this load is lubricated through the bearing, so that the impact load it bears plays a buffering role.

anti-wear: adding lubricant to the rubbing surface can reduce the friction coefficient, thus reducing the friction resistance, saving energy consumption and reducing wear: the lubricant between the rubbing surfaces can reduce the wear caused by abrasive wear, surface fatigue and adhesive wear.

Reference: Baidu Encyclopedia-Engine Oil