What are the consequences of not changing the engine oil for 20,000 kilometers?
4 Answers
Under normal circumstances, if the engine oil has not been changed for 20,000 kilometers, the oil quality may deteriorate and no longer provide any protection to the engine. Expired engine oil has adverse effects on engine operation. Engine oil has certain oxidation and water absorption properties, and over time, the moisture content increases, leading to oil degradation and a corresponding decline in performance. Here are the relevant details: 1. Classification of engine oil: Lubricating oils are categorized into full synthetic oil, semi-synthetic oil, and mineral oil. These three types of engine oil differ in quality and have varying service life. 2. Engine oil replacement cycle: Generally, full synthetic oil should be replaced within 10,000 kilometers; semi-synthetic oil should be replaced every 7,500 kilometers, while the lowest-grade mineral oil needs to be replaced within 5,000 kilometers.
I've been driving for over a decade and have seen many friends who, due to laziness or busy schedules, delay changing their engine oil until 20,000 kilometers, only to face serious problems later. Engine oil is like the lifeblood of an engine; if left too long, it thickens and becomes dirty, significantly reducing its lubricating effectiveness. When this happens, engine components such as piston rings and bearings wear out rapidly, leading to abnormal knocking or tapping noises while driving, and a sharp increase in fuel consumption—sometimes by one or two liters per 100 kilometers. More severely, excessive sludge buildup can clog oil passages, impairing heat dissipation and causing the engine to overheat, potentially leading to cylinder scoring. At best, this results in reduced power; at worst, it necessitates major repairs costing thousands or even tens of thousands of dollars. Additionally, degraded oil causes seals to deteriorate and leak, triggering a chain reaction of damage to other parts. My advice is simple: don't delay. Check your oil color every 5,000 to 10,000 kilometers—if it's too dark or thick, change it immediately. It saves both money and hassle in the long run.
My car's maintenance records have always been meticulous, but I've heard many cases from mechanics about the serious consequences of not changing the oil for 20,000 kilometers. When oil cleanliness declines, impurities accumulate, and lubrication fails, it can easily lead to bearing wear or cylinder liner scratches, with increased engine noise being an early warning sign. If driving continues, it may also clog the catalytic converter, cause excessive emissions, and affect annual inspections. In the long run, engine lifespan could be reduced by over 40%, with a high likelihood of premature failure. Additionally, there are safety risks—deteriorated oil has poor heat dissipation, which may cause unexpected engine stalls, especially dangerous on highways. I often remind myself that oil changes aren't just about mileage; driving conditions and oil quality matter too—more frequent changes are needed for city driving with heavy traffic.
As a novice driver, I almost made this mistake last time. Fortunately, I listened to the advice of an experienced driver and changed the oil in time. If you delay until 20,000 kilometers, the oil will degrade like sewage and fail to protect the engine. Common consequences include accelerated wear of components, and you may feel sluggish acceleration or abnormal vibrations; excessive sludge can also cause blockages, leading to lubrication failure and engine overheating or burning out. Even worse, the repair costs can be exorbitant—a major overhaul can cost thousands, far exceeding the few hundred dollars for an early oil change. It may also cause oil leaks, dirtying the underside of the car. In short, the maintenance manual's 10,000-kilometer interval makes sense—don’t follow my example of cutting corners for convenience.
