What level is SM engine oil?
4 Answers
SM grade engine oil is a high-quality grade. Engine oil models include: SG, SH, SJ, SL, SN, etc. The functions of engine oil are: 1. Reduce friction and high temperature; 2. Cool down; 3. Clean and purify; 4. Dampen vibrations; 5. Prevent rust and corrosion. Engine oil, also known as engine lubricant, is composed of base oil and additives. The base oil is the main component of the lubricant, determining its basic properties, while the additives compensate for and improve the deficiencies of the base oil. The method for changing engine oil is: 1. Lift the vehicle with a jack, locate the drain bolt, and loosen it to drain the oil; 2. Unscrew the oil filter and place a container underneath; 3. Replace with a new oil filter and add new engine oil.
Back when I first started driving, I researched motor oil extensively. The API SM grade belongs to the older Service Category S standards, introduced around 2004, primarily designed for basic lubrication protection in older engines. It offers decent oxidation resistance and detergency, making it suitable for early-2000s vehicles, but falls short compared to newer SN or SP grades—especially in fuel economy and wear protection. I often used SM oil in older cars to save money, but noticed significantly louder engine noise; upgrading to SN brought smoother operation, making the engine feel years younger. The key is not to neglect oil change intervals—SM oil tends to sludge up faster, so I recommend changing every 5,000 km or 6 months to prevent premature engine wear. While SM isn’t bad overall, with advancing times, I’d recommend opting for higher-grade oils.
Working with car repairs every day, API SM engine oil is one of the API service categories, a typical old-grade oil. It focuses on basic engine protection and is more suitable for cars manufactured before 2004. Nowadays, newer cars emphasize higher-grade oils like SP or SN, which provide better protection for turbochargers and direct injection systems. A common issue customers face is using SM oil in newer cars, resulting in increased engine noise and higher fuel consumption—more harm than good. I recommend that owners of older cars first check their manuals; if it specifies SL or SM, it might still be usable, but upgrading sooner is better—premium oil can extend engine life and save on major repair costs. Additionally, SM oil performs poorly in extreme conditions, thinning easily in summer heat and causing slow starts in winter, so owners should pay extra attention to temperature changes.
When I helped with my family car's maintenance, I asked the repair shop. API SM oil is an older classification in the API standards, roughly suitable for cars before 2004. It's slightly inferior to newer ones, with decent protection but insufficient cleanliness, leading to faster sludge buildup. Our old car has used SM for years without issues, mainly because we change the oil every 6 months on time; but don't randomly use SM for new cars—the manual now recommends SN or SP to prevent engine problems. When changing oil, check the bottle label to confirm it's SM, and don't buy counterfeit products—good oil can make your car last longer, saving both hassle and fuel costs.
