What is the difference between 0w40 and 5w40 engine oil?

[LaDawson]

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.

[StSamuel]

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.

[DelTessa]

Having worked in the auto parts market for over a decade, I've seen too many cases of wrong engine oil usage. The biggest difference between 0w40 and 5w40 is low-temperature fluidity - 0w provides about 30% faster cold starts in winter compared to 5w. I've tested it in a freezer: at -30°C, 0w40 pours out like salad oil while 5w40 becomes slightly viscous. This difference directly impacts engine lifespan, especially for turbocharged vehicles where cold start wear protection relies on oil flow. Last year when helping a taxi fleet change oil, after switching all Harbin vehicles to 0w40, their engine overhaul rate dropped by 30%. Of course, there's no difference in high-temperature performance during summer - the 40 viscosity rating is completely adequate. If you're south of North China, choosing 5w40 is more cost-effective.

[CoreyLynn]

At the last car modification meetup, discussing engine oil made me realize the hidden details in the 0w40 and 5w40 labels. The number before the W indicates low-temperature performance: 0w is suitable for temperatures as low as -35°C, while 5w only goes down to -30°C—a noticeable difference for friends in the north. I’ve used both oils in my car. During the coldest week at -28°C, the car with 5w40 oil struggled to start for three seconds, while the one with 0w40 fired up instantly. However, the number 40 indicates the same high-temperature viscosity, meaning no difference in engine protection during summer long-distance drives. The money-saving trick lies in temperature zones: for regions above -20°C, 5w40 is perfectly sufficient. If you frequently face extreme cold or drive performance cars, spending a bit more on 0w40 is more worry-free. Also, a reminder for German car owners: older models like the Bora might trigger the oil warning light with 5w40.

[MarianaLynn]

When choosing engine oil for a new car, my engineer friend told me the main difference between 0w40 and 5w40 lies in the first letter. The 0w offers better low-temperature pumpability, forming an oil film to protect the engine instantly during cold starts. Last time, using a borescope, I observed that piston rings using 5w40 long-term had 20% more carbon deposits compared to 0w40. However, under high-temperature conditions, the '40' suffix ensures the same viscosity, maintaining stable oil pressure during aggressive driving. In terms of fuel efficiency, using 0w40 for short city drives can save about 3% in fuel consumption due to reduced friction during cold starts. But this advantage disappears if you frequently drive on highways. Overall, 0w40 is the preferred choice in regions with large temperature variations, while 5w40 offers better cost-performance in areas with mild seasons. For turbocharged cars, 0w40 is recommended as the priority.