Can opened engine oil still be used after one year?
2 Answers
It is not recommended to use engine oil that has been opened for one year. If the engine oil has been stored for a long time and improperly preserved, the chemical components inside will deteriorate. It is advised not to use it to avoid damaging the valve oil seals and the engine. After opening, engine oil should be stored indoors away from light, and the indoor temperature should not be too high. Additionally, it should not be stored for more than three years. Engine oil, also known as motor oil or engine lubricant, is a substance enhanced with additives in base oil, primarily containing anti-wear additives, detergents, dispersants, and multi-grade viscosity index improvers. The main functions of engine oil are to reduce friction and wear on moving parts, and to remove sludge (one of the functions of dispersants) and varnish (the function of detergents) from the engine.
I've been driving for over 20 years and have encountered many oil changes. I really wouldn't recommend using engine oil that's been opened for a year. Once engine oil is opened, even if the cap is tightly screwed on, it will gradually react with moisture and oxygen in the air. Over time, the additives will decompose and become ineffective. I've tried using leftover oil that had been sitting for too long before, and the engine noise became noticeably louder. When I opened it up later, there was sludge inside. The lubrication effect was greatly reduced, increasing engine wear. Although the oil may still look clear on the surface, its internal protective properties are already compromised. So now, if I have leftover oil for more than six months, I dispose of it directly. Saving a hundred bucks isn't worth it when engine repairs could cost thousands.
