Does Mixing Two Types of Engine Oil Have Any Impact?

[OPeyton]

During seasonal maintenance, some car owners are reluctant to drain the remaining engine oil and instead choose to top it up with a certain amount of new oil before continuing to use it. Sometimes, they even mix two different types of engine oil. This mixing is often done blindly, simply combining another type of oil without consideration, which may lead to abnormal smoke from the exhaust pipe, severe wear on the pistons and cylinder liners, and accelerated formation of oil sludge. Mixing Gasoline and Diesel Engine Oil: Although gasoline and diesel engines are both internal combustion engines, and both types of engine oils are formulated from base oils and additives, they have fundamental differences in specific formulations and ratios. For example, diesel engine oil contains more additive components, and even with the same viscosity grade, diesel engine oil tends to have higher viscosity than gasoline engine oil. Mixing different types of lubricants may result in risks such as engine overheating or increased wear during cold starts, which will undoubtedly affect engine reliability. Therefore, car owners are advised to avoid mixing oils for different engine types whenever possible. Mixing Different Brands of Engine Oil: Engine oil is primarily composed of base oils, viscosity index improvers, and various additives combined in an optimal formulation. Even if oils from different brands share the same type and viscosity grade, their base oils or additive components may differ to some extent, such as dispersants, high-temperature deposit inhibitors, rust inhibitors, antioxidants, etc. Mixing oils from different brands may, under certain conditions, form cotton-like substances or particles, leading to clogged oil passages and increased wear.