Can You Mix 5W30 and 5W20 Oils? Safe Mixing Guide & Tips

Explore products we truly believe in, all independently reviewed to save you time and research. If you make a purchase using our links, it helps us keep creating valuable content like this. Learn more about how we support ourselves.

Ever found yourself staring at two different bottles of motor oil, 5w30 and 5w20, and wondering if they could just get along in the same engine? You’re not alone. It’s a question that pops up more often than you’d think, especially when you’re in a pinch and the exact oil grade you need is just out of reach.

We’ve all been there, right? The moment when you’re about to perform an oil change and realize you’ve got a mix of bottles. It seems like a small decision, but it’s one that could have implications for your vehicle. Let’s dive into the heart of this oily dilemma and shed some light on whether mixing these two is a recipe for smooth running or a potential engine headache.

Understanding Motor Oil Viscosity Ratings

Moving from the initial concern about whether mixing 5w30 and 5w20 motor oils is suitable for an engine, it’s crucial to grasp what the numbers in these viscosity ratings represent. These ratings are not just random figures but convey significant information about the oil’s performance in various temperatures.

The “W” in the viscosity rating stands for “winter,” indicating the oil’s performance in cold temperatures. The number preceding the W, such as the ‘5’ in both 5w30 and 5w20, measures how easily the oil flows at cold temperatures. The lower the number, the less it thickens in the cold, making both 5w30 and 5w20 relatively similar in cold conditions.

Following the “W,” the numbers ’30’ and ’20’ represent the oil’s viscosity at engine operating temperature, or essentially, how thick or thin the oil is at high temperatures. A ’30’ viscosity oil is thicker at high temperatures than a ’20’ viscosity oil. This difference impacts how the oil lubricates the engine components under normal operating conditions. The thicker oil, 5w30, offers more lubrication and film strength at higher temperatures, possibly providing better protection for the engine.

Understanding these ratings helps us realize that while 5w30 and 5w20 have similar properties in cold weather, their performance diverges at higher temperatures. This divergence is critical, as the engine relies on oil for protection against wear and overheat, making the choice of oil critical for engine health and performance.

Can You Mix 5W30 and 5W20?

Building on the importance of selecting the correct motor oil, we often encounter questions about mixing motor oils, specifically whether combining 5W30 and 5W20 oils is advisable. Given the viscosity differences at high temperatures, it’s understandable why some might hesitate.

Technically, mixing 5W30 and 5W20 motor oils won’t immediately harm your engine. Both have a starting viscosity of 5 at cold temperatures, ensuring the oil remains fluid enough to start in cold weather. The concern primarily lies in the high-temperature behavior and the oil’s ability to maintain adequate lubrication over the engine’s operating range.

Manufacturers formulate motor oils to meet specific performance criteria, including viscosity stability across a range of temperatures. When you mix oils with different viscosities, such as 5W30 and 5W20, the resulting mixture will have properties that are, to some extent, average of the two. This mix might not provide the optimal protection or performance intended by the vehicle’s manufacturer, particularly under extreme conditions or in engines with tight tolerances.

However, in a pinch, if you’re topping up your oil and the exact grade isn’t available, mixing these two won’t cause immediate damage. The mixed oil will still lubricate the engine, but it’s best to revert to the manufacturer-recommended viscosity at your next oil change. Engine manufacturers design and test engines with specific oil viscosities in mind to ensure longevity and reliability. Constantly using the correct oil not only maintains your engine’s performance but also contributes to its longevity.

In essence, while you can mix 5W30 and 5W20 motor oils without expecting catastrophic failure, it’s not the ideal practice for maintaining engine health. Always aim to use the oil viscosity recommended by your vehicle’s manufacturer to ensure the best performance and protection for your engine.

Manufacturer Recommendations and Warranty Concerns

Moving onto manufacturer recommendations and warranty concerns, it’s essential to underline the importance of adhering to the guidelines set out by your vehicle’s manufacturer regarding oil use. Vehicle manufacturers specify oil types, such as 5w30 or 5w20, based on extensive testing to ensure the engine operates efficiently and remains durable over time. Diverging from these recommendations by mixing different oil viscosities can lead to unforeseen consequences.

Firstly, consider the warranty implications. Most manufacturers demand the use of a specific motor oil viscosity for their warranty to remain valid. If an engine issue arises and it’s discovered that the oil used does not comply with the manufacturer’s specifications, there’s a risk the warranty could be voided. This means any repairs needed might not be covered, leading to potentially substantial out-of-pocket expenses.

Secondly, manufacturers design engine components with a particular oil type in mind. For example, internal clearances and tolerances in an engine that specifies 5w20 might not accommodate the thicker consistency of 5w30 when temperatures rise. As a result, mixing oils and thus altering the expected viscosity could affect engine lubrication, impacting performance and longevity.

Lastly, vehicle manufacturers collaborate with oil companies to develop oils that meet specific performance and protection criteria. This collaboration ensures that the oil does more than just lubricate; it also helps in cleaning engine components and enhancing fuel efficiency. Using the recommended oil viscosity ensures you’re getting the full benefit of the research and development efforts aimed at extending your engine’s life and optimizing performance.

In light of these points, while mixing 5w30 and 5w20 oils isn’t detrimental in the short term, it’s clear that staying within the manufacturer’s guidelines is key to maintaining engine health, warranty validity, and overall vehicle performance. Our advice is to always consult your vehicle’s owner manual or reach out to the manufacturer for the best guidance on which oil to use for your engine.

Considerations Before Mixing Oils

Given the background on oil viscosity ratings and the importance of adhering to manufacturer recommendations, let’s delve into some considerations before mixing 5w30 and 5w20 oils. Understanding these aspects ensures we make informed decisions about our vehicle’s engine health and performance.

First, consider the climate. Engines operate under a range of temperatures, and oil viscosity directly influences engine performance in these conditions. While 5w20 is typically recommended for colder climates due to its thinner consistency at lower temperatures, 5w30 provides better lubrication and protection in warmer climates. Mixing these may not provide the optimal protection across all temperature ranges.

Second, ponder engine age and condition. Older engines or those with high mileage may benefit more from the slightly thicker 5w30 oil, which can better fill gaps and provide enhanced lubrication. If your vehicle’s engine falls into this category, mixing in thinner 5w20 oil might not be the best approach for engine protection.

Third, review your vehicle’s warranty and manufacturer’s guidelines again. While it’s been established that mixing oils of different viscosities might not immediately harm your engine, it could void your warranty or lead to complications not covered by the manufacturer.

Fourth, understand the potential for performance issues. While immediate damage is unlikely, mixed viscosity oils may not provide the optimal balance between fuel efficiency and engine protection, potentially affecting the vehicle’s performance over time.

Lastly, if you find yourself in a situation where mixing is considered, ensure it’s a temporary solution. Prioritize returning to the manufacturer-recommended viscosity at the earliest opportunity. Regular maintenance checks should include ensuring the oil is at the correct level and viscosity for your vehicle’s specific needs.

Addressing these considerations helps us maintain our vehicle’s health and performance, ensuring we enjoy a smooth driving experience for years to come.

How to Safely Mix 5W30 and 5W20

After understanding the importance of motor oil viscosity and considering various factors before mixing, let’s dive into how to safely mix 5W30 and 5W20 oils if you find it necessary. It’s crucial to remember, this practice should be approached with caution and seen as a temporary solution.

  1. Check the Engine’s Oil Capacity: Before proceeding, determine the total oil capacity of your engine. This information is found in the vehicle’s owner manual. Knowing this helps in calculating the mix ratio.
  2. Calculate the Mix Ratio: Aim for a balance that won’t significantly alter the average viscosity. For instance, if your engine holds 5 quarts of oil, using 3 quarts of 5W30 and 2 quarts of 5W20 creates a blend closer to 5W30, suitable for slightly warmer conditions.
  3. Ensure Oil Compatibility: Make sure both oils are from reputable brands and have similar additive packages, especially if they’re synthetic or conventional, to avoid chemical imbalances that might harm the engine.
  4. Mix the Oils: It’s preferable to mix the oils before adding them to the engine. Use a clean container to blend the amounts you’ve decided on, then pour the mixture into the engine.
  5. Monitor Engine Performance: After mixing and running the engine, closely monitor the vehicle for any unusual noises, performance issues, or warning lights. If any problems arise, it’s advisable to change the oil to the manufacturer’s recommended viscosity immediately.
  6. Return to Recommended Viscosity at Next Change: This mixing should be a one-time occurrence. Plan to return to the manufacturer-recommended oil viscosity at your next oil change to ensure optimal engine health and performance.

By following these steps, you can temporarily mix 5W30 and 5W20 motor oils without causing immediate harm to your engine. However, it’s always best to adhere strictly to the manufacturer’s recommendations for oil viscosity to maintain your vehicle’s longevity.


We’ve walked through the nuances of mixing 5W30 and 5W20 motor oils and it’s clear that while it’s not the end of the world if you find yourself in a pinch it’s not a habit you’ll want to get into. Keeping your engine’s health and performance in mind always opt for the manufacturer’s recommended viscosity. Remember mixing oils should only be a temporary fix. Let’s make sure our engines stay happy and healthy by giving them exactly what they need. Here’s to smooth driving and even smoother engine performance!

Related Posts:

Photo of author

Warren A. Holden

Warren A. Holden, the visionary behind Drive Cruise, is a dynamic automotive enthusiast driven by an unwavering passion for cars and a profound desire to create a unique space for fellow enthusiasts.