First of all, the engine oil has two kinds of labels, which are divided into SAE label and API label. "5W-40" is the SAE label, and "SN" and "SL" are API labels. So what do these two labels mean?
S meaning
Represents gasoline engine oil
N meaning
Starting from A
The lower the letter
The higher the quality level
5 meaning
The smaller the number
The better the low temperature fluidity
The more suitable for cold weather
W meaning
Express winter
40 meaning
Represents high temperature resistance of engine oil
Higher value
Higher protection at high temperatures
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