What is the difference between 5w40 and 0w40 engine oil?
3 Answers
5w40 and 0w40 engine oils differ in their low-temperature flow performance: 5w40 oil can flow normally at temperatures as low as -30°C, while 0w40 oil can flow normally at temperatures as low as -35°C. The functions of engine oil are: 1. To reduce friction and high temperatures; 2. To minimize gas leakage and prevent external contaminants; 3. To prevent contact between water, air, acidic harmful gases, and engine components; 4. To cushion the pressure rise in the engine cylinder ports; 5. To clean dirt generated on the working surfaces of components. Engine oil consists of base oil and additives. Base oils are categorized by quality into Group I, Group II, and Group III base oils, with Group I and II being mineral oils and Group III being synthetic base oils. There are various types of additives, and the quantity and quality of additives directly affect the API quality rating of the lubricant.
I've been driving for over twenty years, and choosing engine oil is not something to take lightly. The main difference between 5W40 and 0W40 lies in their low-temperature performance—the first number indicates the oil's flow capability in cold weather. 0W40 maintains fluidity at lower temperatures than 5W40, making it easier to start the engine even in sub-zero conditions, especially suitable for folks in the Northeast or colder regions. Once, I used 5W40 in winter and clearly felt slower starts, with the engine clanking—it just sounded painful. Though 0W40 is a bit pricier, it starts quicker and better protects pistons and gears, reducing wear. In summer, both perform similarly since their high-temperature viscosity is 40, keeping the engine stable at high speeds. My advice: choose based on your location—go for 0W40 in extreme cold, and save costs with 5W40 in warmer areas. And don’t forget regular oil changes—skimping here could lead to costly repairs.
I've been tinkering with cars at home for over a decade and have extensive DIY oil change experience. The key difference between 5W40 and 0W40 lies in cold-start performance - 0W40 flows better at low temperatures, working perfectly even at -35°C, while 5W40 may struggle below -20°C. They share the same high-temperature viscosity, so there's no difference at high RPMs. From my garage oil change tests across seasons: 0W40 ensures smoother engine starts with less noise and eliminates warm-up time; 5W40 suffices for southern summers and saves about five bucks. But for older, high-mileage engines, I prefer 0W40 for extra protection. Always check dipstick regularly - mixing brands causes issues.
