Can motor oils of the same grade but different brands be mixed?
3 Answers
Motor oils from different brands should not be mixed. Oils of different brands and grades are formulated with varying additives to meet the specific working characteristics and environmental requirements of different engines, resulting in differences in viscosity, anti-wear properties, corrosion resistance, anti-knock performance, and volatility. Mixing them may degrade the oil's performance and even cause damage to the engine. Here are the reasons why motor oils should not be mixed: 1. Mixing new and used oil reduces performance. New and used oils should not be mixed. Used oil contains a large amount of oxidative substances, and when mixed with new oil, it accelerates the oxidation and deterioration of the new oil, thereby reducing its effectiveness and service life. 2. Mixing oils can cause turbidity. Oils of different brands and grades should not be mixed. The chemical additives in oils of different brands and grades may react with each other, reducing lubrication effectiveness and producing acidic or alkaline compounds that can accelerate corrosion of engine components.
As a car enthusiast who often tinkers with vehicles, I have to say mixing different brands of the same oil grade is not a good idea. On the surface, they may all be labeled as 10W-30 or similar viscosity grades, but the additive formulations vary drastically between manufacturers—anti-wear agents or detergent dispersants might conflict, forming sludge that clogs oil passages. Once I mixed a bit of different brand oils, and the engine noise noticeably increased in the short term, which really startled me. High-performance oils like full synthetic or semi-synthetic are even more sensitive to this. Long-term mixing can lead to insufficient lubrication, accelerated wear, and even necessitate major engine repairs. Experts recommend sticking to the same oil brand or thoroughly flushing out old oil when switching. Always remember to check the dipstick and API certification—safety first is never wrong.
I drive to work every day and have encountered low engine oil levels a few times. The idea of mixing different brands to save money briefly crossed my mind. Adding a little as an emergency measure might seem feasible in the short term, but the actual risks are significant. The base oils and additives in different engine oils vary greatly, and mixing them can lead to poor lubrication and reduced engine efficiency. A mechanic told me this could cause subsequent issues, such as increased fuel consumption or shorter oil change intervals, ultimately raising costs. It's better to invest in a new bottle of engine oil to avoid long-term damage. Conventional oil, for example, is coarser, and mixing it makes quality control difficult. Regular maintenance is wiser than taking risks—don't lose big for small savings.
