Can You Mix Different Types of Motor Oil?

Mixing motor oils is a question that many drivers face, especially in situations where theyre topping off low oil levels or switching brands. While its possible to mix different types of motor oil, whether its a good idea depends on the kinds of oil involved and your cars specific needs. Below, well explore the ins and outs of mixing oils, what happens when you do it, and when you should avoid it entirely.

1. The Short Answer: Yes, But

You can mix different types of motor oil changesuch as synthetic with conventional, or different brandsbut its generally not recommended unless its an emergency. Mixing oils wont typically cause immediate engine damage, but it can reduce oil performance and long-term engine protection.

2. Types of Motor Oil You Might Mix

Understanding the different types of oils is key to knowing what can be mixed:

a. Conventional Oil

Made from refined crude oil, this is the most basic type of motor oil. It offers decent protection but breaks down faster under extreme heat or cold.

b. Synthetic Oil

Laboratory-engineered for better lubrication and stability, synthetic oil offers superior performance, especially in extreme temperatures.

c. Synthetic Blend

A mix of synthetic and conventional oil, designed to offer better performance than conventional at a slightly lower price than full synthetic.

d. High-Mileage Oil

Formulated with seal conditioners and additives to reduce oil burn-off and leaks in engines with over 75,000 miles.

3. Common Mixing Scenarios and Their Effects

? Synthetic + Synthetic Blend

Safe and compatible. Since synthetic blends already contain synthetic oil, this mixture wont harm your engine.

?? Synthetic + Conventional

Generally safe in small amounts. However, it dilutes the benefits of the synthetic oil, such as longer lifespan and better protection at high or low temperatures.

? Diesel Engine Oil + Gasoline Engine Oil

Not recommended. Diesel oils have different additives (like detergents and anti-wear agents) and viscosity standards. Mixing them with gasoline oil can harm performance or emissions systems unless specifically approved by the manufacturer.

? Same Type, Different Brands

Safe in most cases. Brands may use different additive packages, but base oils are typically compatible. Still, performance may vary slightly.

4. What Happens When You Mix Oils?

Heres what you need to consider:

• Additive Clashing: Different brands use different additives for anti-wear, detergent action, and viscosity control. Mixing them might lead to reduced effectiveness or unintended chemical reactions over time.
  
  

• Diluted Performance: Mixing synthetic with conventional will lower the synthetic oils enhanced temperature and oxidation resistance, shortening oil change intervals.
  
  

• Warranties: If your engine is under warranty, always follow the manufacturers recommended oil type. Using a different or mixed oil could void the warranty if engine damage occurs.
  
  

5. When Mixing Oil Might Be Necessary

Mixing oils may be unavoidable in these situations:

• Emergency Topping Off: If your oil is low and you only have a different type of oil on hand, its better to top off than run low. Running low on oil can cause catastrophic engine damage.
  
  

• Long Trips: If youre traveling and cant find your regular oil brand or type, mixing in a compatible substitute is acceptable as a temporary solution.
  
  

• Gradual Oil Changes: Some people slowly transition from conventional to synthetic by mixing during oil changes. While this is okay, its not necessary with modern engines, which can usually switch directly to synthetic without issues.
  
  

6. OEM Recommendations Matter Most

Always check your owners manual for:

• Required viscosity grade (e.g., 5W-30, 0W-20)
  
  

• Manufacturer-approved specifications (like API, ACEA, or ILSAC ratings)
  
  

• Preferred oil type (full synthetic, blend, etc.)
  
  

Mixing oils that dont meet these specifications may reduce engine efficiency or cause wear over time.

7. Myths About Mixing Motor Oil

Lets clear up a few common misconceptions:

? Myth 1: Mixing Oils Will Blow Your Engine

Not true. Most modern motor oils are compatible enough that mixing them wont cause immediate damage. The concern is more about performance loss than outright failure.

? Myth 2: You Cant Mix Synthetic and Conventional

While its not ideal, you can mix them. The result is essentially a synthetic blend.

? Myth 3: Oil Brands Arent Compatible

Generally, they are. But if you're using oils from lesser-known brands or specialty formulas (like racing oils), stick with one brand to avoid additive clashes.

8. Mixing Motor Oils: Pros and Cons

9. Best Practices If You Must Mix

• Use similar viscosity grades (e.g., mixing 5W-30 with 5W-30 is safer than 5W-30 with 10W-40)
  
  

• Stick with reputable brands that meet your cars specification standards
  
  

• Avoid mixing oil meant for different engine types, like diesel vs. gasoline
  
  

• Change the oil sooner than usual after mixing, especially if conventional oil is involved
  
  

10. Final Verdict

You can mix motor oils of different types or brands in a pinch, but its best to avoid making it a habit. For optimal performance and engine longevity:

• Stick to one oil type that meets your manufacturers specifications
  
  

• Use full synthetic for the best protection, especially in high-mileage or high-performance engines
  
  

Only mix oils when necessary and follow up with a complete oil change as soon as you can