Can Motor Oils of Different Grades Be Mixed?
2 Answers
Motor oils of different grades should not be mixed. Although the lubricating properties remain unchanged when two different grades of oil are mixed, the composition of the oil will change. Mixing can degrade the performance of the oil and may even cause damage to the engine, so it is not recommended to mix motor oils of different grades. Motor oil serves multiple functions, including lubrication and friction reduction, auxiliary cooling, sealing and leak prevention, rust and corrosion protection, and shock absorption. Motor oil consists of base oil and additives. The base oil is the main component of lubricating oil, determining its fundamental properties, while additives compensate for and improve any deficiencies in the base oil's performance, making them an essential part of the lubricating oil.
I've been in the automotive industry for many years and strongly advise against mixing different grades of motor oil. While they may all appear to lubricate the engine at first glance, their formulations actually vary significantly. The base oils and additives used by different brands can potentially undergo chemical reactions, which may actually reduce lubrication effectiveness. Just last week, a car owner mixed mineral oil with full synthetic oil, resulting in flocculent precipitates forming in the engine. If you must mix in an emergency, stick to oils with the same viscosity grade, keep the total mixture below 20%, and most importantly, get the oil changed immediately. Don't try to save small money during maintenance at the risk of damaging major components - engine repairs cost far more than regular oil changes. This is absolutely not something to be careless about.
