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