Does Motor Oil Degrade Over Time?

Lubricants dedicate themselves to engine parts so that they run effortlessly. Every component added to the oil makes sure it serves the vehicle well without affecting itself. But no matter what, the quality won’t stay top-notch for always. It can be affected whether the oil has been used, unused, opened, or unopened. Now, this can raise a certain question-

Does engine oil break down over time? 

Yes, engine oil degrades over time due to different circumstances like overheating or extreme temperature, oxidation, moisture, and contaminants. Its shelf life increases or decreases based on the type of lubricant, use, maintenance, condition of the engine, and other stuff. 

Let’s know how and why it happens. 

Causes Of Motor Oil Deterioration  

Just like any other thing, lubricants have a shelf life too. Their expiry date depends on several situations so there isn’t any specific answer to it. Now, what causes motor oil to degrade?  

Temperature, air/oxygen, and moisture are the roots of degradation. All of these cause contamination, thermal breakdown of oil, and oxidation that lower the quality of engine oil. 

Contamination Of Motor Oil

Metal wear products and soot are some contaminants that affect the physical and chemical properties of engine oil. It thickens the lubricant to a great extent and causes pumpability issues. 

Thermal Breakdown Of Motor Oil

Engine oil has a specific heat capacity thanks to the metal additives that are used as anti-wear agents. This helps the lubricant absorb heat and makes the parts move smoothly.

However, sometimes, the fluid can get hotter than the recommended temperature. In that case, the thermal conductivity of the engine oil helps it transfer heat to the oil pans so the heat can be dissipated. 

If the lubricant’s thermal conductivity is low, then it can lead to overheating. And this can make motor oil vaporize or decompose. As a result, essential additives will be removed from the engine degrading the quality of the lubricant. 

Oxidation Of Motor Oil

Environmental elements like air and water have oxygen that reacts with oil, causing oxidation and a chemical change. While degrading lubricant, this ends in base oil breakdown, additive depletion, sludge and sediment formation, acid number increase, filter plugging, and oil thickening. 

Shelf-Life Of Motor Oil

How long does engine oil take to degrade? Depending on different factors such as lubricant type, engine condition, temperature, environmental elements, and driving speed, lubricants can last up to 5 years. That’s how long motor oil lasts. However, we are talking about conventional engine oil here. If it’s synthetic oil, it can last about 6 months to 1 year. 

Studies have shown that the oil properties change significantly at over 18,000 miles. But that can still vary based on several factors. 

So, it’s safe to replace the lubricant once the car hits 5,000 to 10,000 miles. Some vehicles can go more than that smoothly with the lubricant intact. But it’s better to check the guidelines or ask the expert. 

5 Signs Of Degraded Motor Oil

Lubricant will surely let you know when it starts to deteriorate. So, how can you tell if motor oil has gone bad? We got 5 signs that act as oil deterioration warnings. 

1. Burnt odor due to a mix of sludge and carbon
2. Dirty and black color.
3. Changed viscosity.
4. Engine vibration and noise due to friction. 
5. Slow acceleration of the vehicle.

Frequently Asked Questions

1. Does Motor Oil Degrade If Not Used?

Yes, motor oil can degrade by just sitting inside the engine. It has a shelf life ranging from 6 months to 5 years. When unopened, it stays good in the bottle until its date of expiration. As it goes past time, different factors such as changes in chemical composition can lower the quality of lubricant. Hence, it won’t work effectively. 

In case the oil has been opened and still not used, it can stay good for 5 years. However, exposure to environmental elements can degrade the engine lubricant. 

2. What Happens If You Don’t Change Your Oil For 2 Years?

When you don’t change motor oil for 2 years, it starts to solidify or gel in the engine and becomes sludge. Such affected oil can’t get into all the engine parts which leads to oil starvation in the valve train components, camshafts, bearings, and crankshafts. 

So, you must replace the lubricant at least once every 2 years. 

3. How To Prevent Motor Oil Oxidation?

You need to follow some simple steps to prevent motor oil oxidation. Just make sure the bearing seals are in good shape. The pressure of reservoir system shouldn’t be exceeded. Plus, consider using gas with low reactivity since it can help prevent air from getting inside. Nitrogen can be a good option. 

Final Words

While the quality of motor oil can change based on various circumstances, you can make it last a good time by following some simple steps. Just make sure the lubricant isn’t exposed to extreme temperatures since it can cause dilution. Plus, keep the oil away from heavy air otherwise it may lead to condensation buildup. 

For the maintenance routine of your vehicle to a T. Use the recommended parts, lubricants, and fluids. That’s how you can stop motor oil from deteriorating quickly. 

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