Can engine oil older than 5 years be used?

[JacksonLee]

Engine oil older than 5 years cannot be used. The functions of engine oil are: 1. To reduce friction between the cylinder liner, piston rings, and camshaft; 2. To form a seal between the piston rings and pistons, reducing gas leakage and preventing external contaminants from entering; 3. To adhere to the surfaces of parts, preventing contact with water, air, acidic substances, and harmful gases; 4. To alleviate the load on pistons, piston skirts, connecting rods, and crankshaft bearings; 5. To flush away carbon deposits, sludge, and worn metal particles from engine parts through the flow of the lubricating oil. The method for changing engine oil is: 1. Lift the car, remove the undercover, and place a container under the drain plug; 2. Unscrew the drain plug, use an air gun to blow into the oil filler port for two minutes, then tighten the drain plug and wipe it with a tissue to check for leaks; 3. Reinstall the undercover, lower the car, and add new oil through the filler port.

[AlainaLee]

From the perspective of automotive maintenance experience, engine oil over five years old is really not recommended for use. Once opened, engine oil can be stored for a maximum of one year. Even if the seal remains unbroken, the additives will precipitate and decompose after five years. I once saw old engine oil in a repair shop that had clumped up like jelly. If such oil is added to the engine, the lubrication effect will be greatly reduced, and it may even clog the oil passages. Especially in fully synthetic oils, anti-wear components are prone to failure, turning into black gel at higher temperatures. Engine repairs can easily cost thousands, so saving a hundred bucks on old oil could end up costing much more. It’s always safer to buy oil with a fresh production date.

[OCharles]

I've reviewed technical documents from many oil manufacturers, which clearly indicate a shelf life of typically four to five years. Over time, the base oil oxidizes and thickens, while the detergents and dispersants lose effectiveness. Some think unopened oil is fine, but plastic containers slowly allow air permeation, and humidity changes can cause moisture ingress, leading to oil emulsification and rust. Formulas from five years ago also lack the wear resistance of today's more environmentally friendly blends. For turbocharged models, extra caution is needed—high temperatures and pressures can turn degraded oil into an asphalt-like substance. That's why I only use oil within three years of production.

[BrookeLee]

I've had personal experience with expired engine oil. Last year while cleaning out the garage, I found half a case of 6-year-old oil - the bottle's sealing rings had become brittle. When I tried pouring it out, the color was as dark as cola with a sour smell. You should know that fresh oil should be transparent amber in color. This aged oil was full of acidic substances generated by oxidation. Putting it in an engine would not only accelerate piston ring wear but also corrode metal components. Nowadays, an oil change service only costs a few dozen dollars - it's really not worth risking engine seizure to save such a small amount.