Can engine oils of different brands be mixed?
2 Answers
Engine oils from two different brands should not be mixed because the additives used in different brands of engine oil vary and can cause chemical reactions, leading to the oil becoming thicker or thinner, partially losing its lubricating properties. Mixing different brands of engine oil can result in: 1. Layering, turbidity, and deterioration of cleaning ability; 2. Abnormal exhaust emissions, as mixing different brands may cause unusual smoke from the exhaust; 3. Formation of sludge, which reduces the cooling effect of the lubricant, leading to higher engine temperatures and potential malfunctions; 4. Accelerated wear, as mixing oils can significantly alter their anti-wear properties, damaging the oil film and increasing the risk of wear between the piston and cylinder wall, potentially leading to piston ring breakage in severe cases.
I've seen many friends' cars have this issue because they were either lazy or trying to save money by mixing different brands of engine oil. Honestly, this is really not a good idea. The additive formulations in engine oils vary greatly. For example, Shell's detergents mixed with Castrol's anti-wear agents could cause chemical reactions, forming sludge that clogs oil passages. My old car fell victim to this - after mixing oils, the engine noise increased dramatically, sounding like a tractor, and the repair revealed damage to the lubrication system. In an emergency, mixing a small amount of different oil might be acceptable, but you should switch back to the same type as soon as possible. Don't cut corners in regular car maintenance - stick to one brand of engine oil to protect engine lifespan and reduce failures. It's best to choose oil according to the manual's recommended type. Synthetic oils have better compatibility but aren't foolproof either, and oil change intervals should be followed precisely.
