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What does SM in engine oil mean?

2 Answers

StAnthony

07/25/25 3:31am

SM in engine oil refers to the API oil quality grade. API is the abbreviation for the American Petroleum Institute. The API grade represents the quality grade of engine oil, using simple codes to describe the working capability of engine oil. It is divided into SA, SB, SC, SD, SE, SF, SG, SH, SJ, SL, SM, and SN grades, with the later letters indicating higher grades. The main components of engine oil are: 1. Base oil: The main component of lubricating oil, determining the basic properties of the lubricating oil; 2. Additives: They can compensate for and improve the shortcomings of the base oil's performance.

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StAxel

08/10/25 5:01pm

I've driven quite a few cars, and initially, I didn't understand that SM label on motor oil at all. Later, I learned it's a performance standard for gasoline engine oils set by the American Petroleum Institute (API), mainly applicable to post-2004 vehicles. SM stands for high-performance protection, effectively reducing carbon deposits and metal wear inside the engine, especially maintaining oil film stability under high temperatures, preventing premature engine failure. I remember using older SL-grade oil before, which resulted in louder engine noise and smoke. Switching back to SM made things much smoother. Now, for every maintenance, I follow the manual's recommendation and choose SM or higher SN-grade oil to ensure lubrication and cleaning capabilities match modern engine designs. Don't underestimate this label—using lower-grade oil can shorten engine life and lead to costly repairs. I recommend regularly checking the oil grade for peace of mind.

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