What is the difference between 30 and 40 engine oil?
2 Answers
30 engine oil and 40 engine oil have the following differences: 1. 40 engine oil has higher viscosity than 30 engine oil. 2. 40 engine oil is suitable for higher maximum temperatures than 30 engine oil. 3. 30 engine oil has better fluidity than 40, which can reduce fuel consumption and dissipate heat from the engine faster. 4. 40 engine oil has better oil stability than 30 under extremely high-temperature conditions of the engine. Here is some relevant information about engine oil: 1. The grade after the oil classification indicates its viscosity specification. "W" stands for Winter, and the smaller the number before it, the better the low-temperature fluidity of the oil, indicating a lower usable environmental temperature and better engine protection during cold starts. 2. Oil classification uses a combination of two letters. The "S" series represents oil for gasoline engines, with general specifications ranging from SA to SN (in alphabetical order, but without SI). Each subsequent letter indicates better oil performance than the previous one, with more additives in the oil to protect the engine.
I've noticed the difference in engine oil during my daily commute. The 30-grade oil has lower viscosity, making it smoother under normal temperatures like in spring and autumn, with better fuel efficiency, quicker engine starts, and less noise. Switching to 40-grade oil feels thicker, providing better engine protection during summer or high-temperature conditions, especially on long highway trips—preventing overheating and delivering a deeper, more stable engine sound. However, 40-grade oil may be harder to start in cold winters and slightly less fuel-efficient. My experience suggests: consider the season and driving habits—30-grade is sufficient for daily commutes in temperate cities; if you often drive in hot regions or love road trips, prioritize 40-grade. Also factor in your car's age—older cars benefit from 40-grade for reduced wear. In short, choosing the right oil extends engine life, saves money, and gives peace of mind.
