Engine Maintenance

16 Myths and Facts About Engine Oil: What Every Car Owner Should Know

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I think we’ve all encountered numerous myths surrounding engine oil, often leading to confusion among car owners.

Understanding the truth about engine oil is crucial for the maintenance and longevity of your vehicle. In this comprehensive guide, I’ll debunk common myths and highlight the facts about engine oil, ensuring every car owner is well-informed.

The Importance of Engine Oil

Engine oil is the lifeblood of your vehicle. It lubricates moving parts, reduces friction, helps seal piston rings, cools the engine, and prevents rust and corrosion. Misconceptions about its use can lead to poor performance and even costly repairs.

1. Myth: Oil Should Be Changed Every 3,000 Miles

  • Fact: Modern engine oils and cars are designed to last longer. Most vehicles can go 5,000 to 7,500 miles, and some even 10,000 miles, between oil changes. Always follow your manufacturer’s recommendation, which is based on the engine design and oil type.

Note: unless the manual states to change it sooner, I never surpass 7,500 miles. I may be old fashion but I think that’s enough wear and tear for any oil, no matter the brand or quality.

2. Myth: Synthetic Oil Causes Leaks in Older Engines

  • Fact: This myth stems from the early days of synthetic oils. Modern synthetic oils are fully compatible with older engines and do not cause leaks. In fact, they can offer better protection and performance than conventional oils, even in older models.

3. Myth: Dark Oil Indicates It’s Time for a Change

  • Fact: Dark oil isn’t necessarily a sign that it needs to be changed. Oil darkens as it does its job of cleaning the engine. The best way to know when to change your oil is to follow the service interval recommended by your vehicle manufacturer.

4. Myth: You Must Use the Same Type of Oil Every Time

  • Fact: While it’s generally best to stick to the type and viscosity of oil recommended by your manufacturer, switching between synthetic and conventional oil isn’t harmful to your engine, as long as the oil meets the vehicle’s specifications.

5. Myth: Engine Oil Additives Improve Performance

  • Fact: Most commercial engine oils already contain a blend of additives optimized for your engine’s performance. Additional additives are usually unnecessary and can sometimes upset the balance, leading to reduced effectiveness.

6. Myth: More Frequent Oil Changes Mean Better Engine Performance

  • Fact: Changing oil more frequently than recommended doesn’t necessarily improve engine performance. It can be a waste of money and resources. Stick to the recommended intervals for optimal performance and efficiency.

7. Myth: If Oil Levels Are Low, There Must Be a Leak

  • Fact: Low oil levels don’t always indicate a leak. Engines can consume oil, especially high-performance engines or those with higher mileage. Regularly check your oil level and top up if necessary.

8. Myth: A Flush Is Needed When Switching Oil Types

  • Fact: When changing from conventional to synthetic oil (or vice versa), a flush is not typically necessary. Modern oils are compatible with each other. However, ensure the oil change includes a new filter.

9. Myth: Thicker Oil Always Provides Better Lubrication

  • Fact: Thicker oil doesn’t necessarily equate to better protection. Using oil with a viscosity higher than your manufacturer’s recommendation can actually harm your engine by creating excess resistance and reducing efficiency.

10. Myth: Oil Should Always Be Changed Before a Long Trip

  • Fact: If your oil isn’t due for a change, it’s usually not necessary to change it before a long trip. However, it’s always a good idea to check your oil level and top it up if it’s low.

11. Myth: Changing Oil Brands Damages the Engine

  • Fact: There is no harm in changing oil brands as long as the oil meets the specifications and viscosity grades recommended by your vehicle’s manufacturer. Modern engine oils are formulated to be compatible with each other.

12. Myth: Once You Switch to Synthetic Oil, You Can’t Go Back

  • Fact: You can switch between synthetic and conventional oil as needed, and it won’t harm the engine. The most important aspect is to use the right grade and specification of oil as recommended by the vehicle manufacturer.

13. Myth: Oil Never Wears Out, Only Gets Dirty

  • Fact: While contamination is a significant reason for oil degradation, oil also breaks down chemically over time. High temperatures, combustion byproducts, and other factors contribute to the oil losing its effectiveness, necessitating a change.

14. Myth: Synthetic Oil Causes More Engine Sludge

  • Fact: Synthetic oil does not cause sludge build-up. In fact, synthetic oils can be better at resisting sludge formation due to their improved stability and often contain detergents that help keep the engine clean.

15. Myth: Oil Filters Don’t Need to Be Changed Every Time

  • Fact: It is generally recommended to change the oil filter with every oil change. Old filters can contain contaminants and sludge that can mix with the new oil, diminishing its effectiveness and potentially harming the engine.

I always change the oil filter when changing oil. The economy of not doing it every time is not worth the risk!

16. Myth: All Synthetic Oils Are the Same

  • Fact: There are variations in the quality and formulation of synthetic oils. Different brands and types offer varying levels of protection, performance, and longevity. It’s important to choose a high-quality oil that meets the specifications required for your vehicle.


Understanding the myths and facts about engine oil is essential for every car owner. Proper knowledge ensures that your vehicle gets the right care, enhancing its performance and longevity. Always refer to your vehicle’s manual for specific recommendations and consult with a trusted mechanic if you have concerns.

Remember, when it comes to engine oil, more informed decisions lead to better vehicle health and performance.

Car enthusiast. I am dedicated to maintaining my cars as best as I can. I love things that work, and I love keeping them in a good state.

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