What does the oil viscosity 10w40 mean?

1 Answers
VanCassandra
07/29/25 4:07pm
Oil viscosity 10w40 refers to: the 'w' stands for winter, the number 10 indicates the oil viscosity under low-temperature conditions, and the last number 40 represents the viscosity index under high-temperature conditions. The parameters of engine oil consist of two parts: the classification and viscosity specifications. The oil quality level ranges from SA to SN, with each increment in the letter indicating better performance than the previous one. Engine oil is the lubricant for the engine, composed of base oil and additives, and it serves to lubricate and reduce friction, assist in cooling, seal against leaks, prevent rust and corrosion, clean, and cushion shocks.
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