What is the difference between 0w40 and 5w40 engine oil?
2 Answers
The difference between 0w40 and 5w40 engine oil lies in their state at low temperatures: 0W40 means the oil remains liquid at minus forty degrees Celsius and will solidify below that temperature; 5w40 means the oil remains liquid at minus thirty-five degrees Celsius and will solidify below that temperature. W40 indicates a viscosity range between 12.5 and 16.3, where 0 represents minus forty degrees Celsius and 5 represents minus thirty-five degrees Celsius. The number before W indicates low-temperature tolerance—the smaller the number, the lower the low-temperature viscosity and the better the low-temperature fluidity. The number after W represents the SAE viscosity range—the larger the number, the thicker the oil, and the higher the summer temperature it can withstand.
That day I helped my elderly neighbor choose engine oil and discovered the key difference between 0W40 and 5W40 lies in low-temperature performance. The number before the W indicates cold-weather viscosity - 0W can withstand -35°C while 5W only goes down to -30°C. During my last business trip to Northeast China at -32°C, cars using 5W40 had obvious starting difficulties with engine knocking sounds, whereas 0W40 worked smoothly. However, both share the same high-temperature protection (the 40 rating), performing equally well during summer highway driving. If you live in southern regions, 5W40 is sufficient and more economical; but for northern areas especially Heilongjiang province, 0W40 is mandatory. One misconception is thinking 0W40's higher price is just marketing hype - actually it uses superior base oil with better low-temperature protection, being particularly friendly to new car engines.
