Does Mixing Two Types of Engine Oil Have Any Impact?
3 Answers
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.
I've always considered engine oil maintenance crucial. Years ago, I accidentally mixed a new can of oil with old residue in my car. Within days, the engine became noticeably louder with sluggish throttle response. A mechanic later diagnosed it as lubrication deficiency caused by viscosity mismatch, which accelerated wear. Since then, I strictly use identical oil specifications – preferably the same brand and grade like SAE 5W-30 – to maintain consistent protection. Engine oil primarily lubricates, cools, and cleans internal components. Mixing different formulations risks foaming or sludge formation, potentially doubling wear rates and shortening engine lifespan. Always use full cans of identical oil during changes. In emergencies, temporarily topping up with closely matched specifications is acceptable, but arrange a complete oil change immediately. Never compromise on this – penny-wise here could prove pound-foolish.
From a daily driving perspective, mixing two types of engine oil can indeed have significant impacts. I've seen many people casually top up with cheaper oil to save money, but this can substantially increase internal engine friction, potentially accelerating component wear within just ten days. Engine oil is like the lifeblood of a car—each formulation has its unique properties. For instance, some synthetic oils have higher viscosity, and mixing them may fail to achieve optimal lubrication, leading to engine overheating or abnormal noises. Worse still, poor compatibility can accelerate sludge buildup, requiring costly full component replacements during repairs. Personally, I recommend ensuring oil consistency during regular maintenance by using the same brand as the old oil, preferably the manufacturer-recommended specification. If accidental mixing occurs, change the oil promptly to minimize risks—safety first is the golden rule.
