Is it okay to mix 5w30 and 5w40?
2 Answers
5w30 and 5w40 should not be mixed. Reasons why 5w30 and 5w40 cannot be mixed: Different grades of engine oil have varying performance characteristics. Additionally, engine technical requirements differ among manufacturers, leading to different viscosity requirements for the oil. Effects of mixing 5w30 and 5w40: It increases the engine's operating resistance, resulting in insufficient engine power. Prolonged mixing can affect the engine's lifespan and also increase fuel consumption. Correct oil selection method: A comprehensive analysis should be conducted based on the vehicle's driving environment, the owner's driving habits, and the vehicle's maintenance manual to select the appropriate oil viscosity for better engine protection.
I deal with car repairs quite often, and while mixing 5w30 and 5w40 oil isn't recommended, it's not catastrophic. The first number, 5w, indicates the same low-temperature viscosity for both, while the 30 and 40 represent differences in high-temperature viscosity. Mixing them can lead to unstable oil viscosity—potentially too thin at high temperatures, causing insufficient lubrication, or too thick, increasing fuel consumption. A small mix isn't a big issue, but prolonged or large-scale mixing can accelerate engine wear or cause cold-start difficulties. Engines are finely tuned for specific oils, and mixing disrupts this performance balance. In an emergency, a small top-up is acceptable as a temporary measure, but switching to a uniform type as soon as possible is best. Sticking to the manufacturer's recommended oil ensures longer-lasting protection—don't cut corners on maintenance to save a little money. Develop a habit of regular oil checks to avoid such mishaps.
