Does it matter if the engine oil hasn't been changed for a year and a half, with low mileage?

[LaEvan]

Even the best engine oil will deteriorate after one year of use. Full synthetic oil should be replaced even if the mileage hasn't been reached. The impacts are as follows: 1. Possible insufficient oil volume: The engine continuously consumes oil during operation, though at a relatively slow rate. As long as there's no oil burning, oil shortage generally won't occur within the normal oil change interval. However, in certain situations like vehicle deceleration, bumpy roads, or body tilting, the oil pump may not be able to draw oil properly. 2. Accelerated oil aging: Engine oil not only provides lubrication but also cooling. Although the heat absorbed by the oil is ultimately dissipated through the engine and coolant, insufficient oil volume reduces the efficiency of heat dissipation, potentially leading to higher oil temperatures and faster oil degradation. 3. Increased engine sludge: Prolonged oil change intervals result in reduced oil volume while the engine continues to operate, generating particles continuously. These particles keep dissolving in the oil until the oil becomes increasingly viscous. 4. Potential oil filter failure: The oil filter is designed to remove impurities from the oil. After leaving the oil pump, the oil passes through the filter before reaching components requiring lubrication. After lubrication, the oil returns to the oil pan and is drawn back into the oil pump, passing through the filter again.

[RosalieMarie]

As a veteran driver with twenty years of experience, I must say that not changing the engine oil for a year and a half even if the mileage is low does have an impact. I remember my first car, which had a similar situation where the oil wasn't changed in time, and the engine started making squeaking noises. Upon inspection, the oil was found to be oxidized and turned black. Over time, engine oil absorbs moisture, contaminants, and breaks down additives inside the engine, losing its lubrication and cooling effectiveness. Even if you drive less, prolonged parking or frequent short trips can accelerate oil degradation, leading to sludge buildup that clogs oil passages. This increases internal engine friction, potentially damaging pistons or bearings, and in the long run, results in costly repairs. I recommend changing the oil at least once a year—regular maintenance is the key to protecting your car. Don't just wait for the mileage; time is more crucial. Go check your engine oil condition now to prevent potential issues.

[MacTaylor]

From a scientific perspective analyzing engine oil issues, I understand time is the critical factor. Engine oil consists of base oils and additives designed to degrade over time. Not changing it for a year and a half, even with low mileage, subjects the oil to thermal cycles and air exposure that trigger oxidation reactions, depleting additives and causing acidification that corrodes internal components. Moisture accumulation emulsifies the oil, reducing viscosity and detergency, compromising lubrication. While synthetic oils resist oxidation slightly better, manuals generally recommend 12-month intervals as aging is inevitable. During inspection, placing a drop on paper—if it spreads too quickly or appears brown—indicates deterioration. Timely replacement protects the engine from long-term wear, prevents increased oil consumption, and maintains cost-effective vehicle health.

[VincentLee]

I believe delaying oil changes can pose safety and economic risks. Going a year and a half without changing the oil when mileage is insufficient leads to oil aging, reduced lubrication, rough engine operation, increased friction, and potential unexpected failures. A small oversight like skipping an oil change may only cost a few hundred yuan, but a major engine overhaul could result in thousands of yuan in losses and inconvenience from being without a vehicle. The owner's manual emphasizes time intervals to prevent sludge formation. Taking risks to save small amounts of money isn't worth it—regular maintenance is the wise choice. Checking the oil every six months or year provides greater peace of mind.

[BradyFitz]

Frequent stop-and-go traffic in urban driving puts more strain on engine oil. Even with low mileage over a year and a half without an oil change, short trips prevent the oil from fully warming up, accelerating acidification and moisture buildup. Aged oil loses effectiveness, causing sluggish acceleration and increased fuel consumption. During city traffic jams, sludge can clog filters and damage components. For urban commuter cars like mine, it's recommended to change the oil at least once a year using high-quality synthetic oil to extend engine life and avoid issues through timely maintenance.

[McSteven]

Overall, not changing the engine oil for a year and a half does have negative impacts. Over time, engine oil deteriorates, losing its cleaning and lubricating properties, which accelerates engine aging. Whether mineral or synthetic, aged oil increases friction, fuel consumption, and potential damage. Climatic factors, such as high humidity, can accelerate degradation. It is recommended to check the oil's color and viscosity; if it appears too dark or thin, replace it immediately. Regular maintenance should follow the intervals suggested in the manual, such as changing the oil every 12 months, to ensure engine reliability. Periodic maintenance involves small expenses to avoid major issues, maintaining vehicle performance for long-term benefits.