What's the difference between 5w30 and 5w40 engine oil?
2 Answers
The differences between 5W-30 and 5W-40 engine oils are as follows: 1. Different viscosity: 5W-30 and 5W-40 oils have different viscosities, with 40 being slightly higher. This means that 40 has higher fuel consumption. 2. Different performance at low temperatures: 5W-30 performs better in low-temperature conditions. This is because the viscosity of 5W-30 is significantly better than that of 5W-40 in low-temperature conditions. 3. Different performance at high temperatures: Under high-temperature conditions, 40 offers better stability. Therefore, if working under prolonged high-temperature conditions, 40 is preferable. For example, in summer, but it should be clarified that even in the hottest summer at the equator, the high-temperature characteristics of 5W-30 are sufficient.
I've done quite a bit of research on this. Both 5W30 and 5W40 are multi-grade oils, where the 'W' stands for winter, meaning they have similar fluidity in cold temperatures. The key difference lies in the numbers after—30 and 40. The 30-grade oil is thinner at high temperatures compared to the 40-grade. For example, during summer traffic jams when engine temperatures soar above 100 degrees, the 40-grade oil forms a thicker protective film. Older engines with wear benefit more from 40-grade, while newer cars are better off with 30-grade for fuel efficiency. I've personally used 40-grade oil and noticed it takes noticeably longer to warm up in winter—usually an extra 20-30 seconds. Of course, always check your owner's manual; some German cars specifically require 40-grade. Driving habits matter too—if you're heavy on the throttle, 40-grade offers more peace of mind.
