Will it have an impact if the engine oil is not changed for over a year?

[VanAlexandra]

Not changing the car engine oil for a long time will significantly reduce its sealing, lubrication, and cooling effects. The impurities in the oil can wear internal components, thereby affecting the engine's lifespan and making it more prone to malfunctions, leading to safety hazards. The following are specific introductions about the functions of engine oil: 1. Lubrication: Dry friction between metals can cause surface damage to metal parts, hence the need for the lubricating effect of engine oil for protection. With the lubrication of engine oil, metal parts can avoid direct contact, instead floating on the lubricating oil. This is commonly referred to as the "oil film bearing" effect. 2. Cleaning: After prolonged engine operation, metal burrs inevitably fall off due to friction. If these burrs fall off, they may threaten other metal surfaces. Therefore, it is essential to rely on the flushing action of the engine oil to "carry away" these metal burrs. 3. Cooling: The interior of the engine operates under high temperatures. While the cylinder relies on the cooling system for cooling, certain internal components cannot depend on the cooling system and can only dissipate working heat through the circulation of engine oil.

[StNova]

I remember the mechanic specifically reminded me about this during the last car maintenance. When engine oil is used for over a year, the additives inside start to degrade, and the lubrication effectiveness plummets. The engine operates under high temperature and pressure, and old oil flows slowly while being prone to clumping. Over time, sludge deposits accumulate on the piston rings, and you can hear abnormal dry friction noises during cold starts. What's worse, the buildup of acidic substances accelerates metal corrosion, with the valve guides being the most vulnerable. Moreover, for cars parked for extended periods, the oil absorbs moisture from the air, and water mixing into the oil circuit actually increases wear. My old car went a year and a half without an oil change, and later the cylinder head needed major repairs. Now I absolutely dare not slack off.

[BenjaminDella]

Cars, like people, require regular maintenance and oil changes, as I've learned the hard way. Overused oil loses almost all its cleaning properties, leaving combustion residue and carbon deposits clogging the oil pan filter screen. Over time, this blocks the entire lubrication system's circulation. Mineral oil starts emulsifying after just ten months, while synthetic oil can't withstand oxidation beyond fourteen months—that's when the dashboard warning light could come on at any moment. This is especially true for vehicles that frequently make short trips, where constant engine temperature fluctuations make oil-water mixtures more likely, eventually leading to abnormal camshaft wear. My neighbor tried to save a few bucks by skipping oil changes, only to end up with a blown bearing mid-drive and an 8,000+ yuan engine overhaul.

[LaEvangeline]

Not changing expired engine oil can cause serious damage to your car. The first casualty is the loss of anti-wear properties—critical components like crankshaft bearings and connecting rod bushings rely entirely on oil film protection. Aged oil with imbalanced viscosity leads to direct metal-on-metal contact. Additionally, the failure of rust inhibitors means the oil pan can develop rust spots in just three months in humid southern regions. I’ve personally experienced this: after 12 months without an oil change, the oil filter was clogged with gummy deposits, and there were signs of blockage in the fuel lines. With today’s heavy urban traffic and frequent engine start-stop cycles, the strain on the engine is even worse. This is definitely not an area to cut corners.

[DelEmmett]

Car manufacturers' recommended oil change intervals are well-founded. By the tenth month of oil usage, viscosity index improvers degrade most rapidly, making cold engine starts particularly strenuous. Not to mention, after exceeding one year, base oil begins to crack and can form lacquer deposits on cylinder walls under high temperatures. My family car last year, delayed for thirteen months due to pandemic lockdowns, revealed sludge-jammed chain tensioners upon engine disassembly—the mechanic just shook his head. Turbocharged vehicles suffer even worse, as their bearings rely entirely on oil for high-temperature cooling, where aged oil tends to coke up and seize the turbo. Now, I'd rather change it half a month early.