The main difference between 5W-20 and 5W-30 oil is thickness at operating temperature — 5W-20 is thinner and improves fuel economy, while 5W-30 is slightly thicker and offers better engine protection under heat and load.
Both oils perform similarly during cold starts, but choosing the right one depends on your engine, driving conditions, and climate—not just the numbers on the label.
In this article, we’ll see how these multigrade oils compare. We’ll also look at a few related queries, including whether you can use 5W-30 instead of 5W-20 or if you can mix the two.
This Article Contains:
- 5W20 Vs 5W30 Oil: What’s The Difference?
- 5W20 Vs 5W30: Which Oil Is Better?
- Should You Switch Between 5W-20 and 5W-30 Seasonally?
- 4 FAQs About 5W20 Vs 5W30 Oil
Let’s get started!
5W20 Vs 5W30 Oil: What’s The Difference?
5W-20 and 5W30 motor oil are winter viscosity grade oils primarily recommended for older engines and light-duty use. These oils are best utilized in colder temperatures.
Both oils exhibit the properties of the SAE 5W winter oil type, but here’s how they’re different:
A. Operating Temperature
A multi-grade oil is graded using the “XW-XX” format.
Here, the ‘W’ stands for ‘Winter,’ the number before it denotes the oil’s viscosity under 0°C (32°F), while the numbers after it represent the viscosity at 100 °C (212°F).
As both these oils have a winter viscosity of ‘5W’, they’re a great winter viscosity grade oil (the lower the number is, the better the oil performs in cold temperature settings).
When it comes to their higher operating temperature performance, 5W30 motor oil performs slightly better than 5W-20 and is a thicker oil than its counterpart.
5W30 motor oil would be more robust and not break down very easily at a higher temperature. Thus, it will protect your engine parts better under moderate oil pressure and high temperature settings.
B. Gas Mileage
Generally, lower viscosity (thinner oil) provides better fuel efficiency for your car.
How?
At normal operating temperature, a lower viscosity oil will provide a thinner barrier of protection between your engine parts, thus reducing friction and improving the engine performance. This impacts your car’s fuel efficiency and gas mileage.
5W-20 oil, being the lower viscosity oil (thinner oil) than 5W-30, might help boost your fuel economy. And although you may not notice a vast difference, it does add up over time.
However, remember to always use the motor oil recommended by your engine manufacturer or mechanic.
Even though 5W-20 motor oil is good for fuel economy, replacing your regular oil with it can mean more harm than good for your engine. 5W-20 engine oil is only ideal for low to moderate temperature use in colder climates.
So does that mean 5W-20 oil is better than 5W-30 oil?
Let’s find out.
5W20 Vs 5W30: Which Oil Is Better?
Neither of the two oils is any better or worse than the other. It all depends on your engine requirements and car type.
When choosing the right multigrade engine oil for your car, you should consider two factors:
- The temperature at which you regularly drive your car (whether you drive in colder temperatures or hotter climates)
- Your engine’s recommended oil viscosity grade
Although some cars do allow some flexibility in engine oil options, most have a recommended viscosity grade. This is because the engines are tuned to run on a certain oil viscosity, and changing that could affect your engine’s performance.
Ideally, 5W-30 oil is perfect for people who drive in seasonal or hotter climates. It has a better viscosity index than 5W-20 oil and is more versatile in terms of its warmer temperature range. You’ll get better protection with 5W 30 oil in cold as well as hotter climates.
5W-20 oil is best for those who live in colder climates with low temperatures. It can be used for light-duty applications, for engines that do not reach very extreme temperatures. 5W-20 oil provides excellent start-up performance in colder temperatures.
NOTE: Older vehicles may need a high mileage variant of their regular oil (5W-20 or 5W-30). In this case, the high mileage oil better protects the engine at extreme temperatures from friction and engine drag.
But what if your driving conditions change throughout the year?
Should You Switch Between 5W-20 and 5W-30 Seasonally?
In some cases, switching between 5W-20 and 5W-30 based on the season can make sense—but only if your engine supports both.
Here’s how to decide:
A. When Switching Makes Sense
- You live in regions with large temperature swings (very cold winters, hot summers)
- Your owner’s manual allows multiple viscosity options
- Your driving conditions change (light winter driving vs heavy summer use)
B. When to Avoid Switching
- Your manufacturer specifies only one oil grade
- Your engine is newer and optimized for a specific viscosity
- You’re unsure about compatibility
C. Climate-Based Decisions
- Colder climates → both oils perform similarly at startup, so the choice depends on usage
- Warmer or high-load conditions → 5W-30 offers better protection
If your engine allows flexibility, seasonal switching can help balance efficiency and protection—but always follow manufacturer recommendations first.
Now that you know when switching makes sense, let’s look at some common questions about using these oils.
4 FAQs About 5W20 Vs 5W30 Oil
Here are the answers to a few queries on 5W-20 vs 5W-30 oil:
1. What Happens If You Use 5W-30 Instead Of 5W-20 Oil?
You can use 5W-30 oil instead of 5W-20 oil if your engine allows for it. The safest way to make sure that it does is to consult your owner’s manual.
If it doesn’t, you’re putting your engine at risk for engine damage and reduced performance. This is because exposing your engine to slightly thicker oil than it’s used to leads to more friction. Your engine has to work harder to perform its duties with the added resistance of the thicker oil.
The increased friction from heavier oil can slow your internal combustion engine and cause problems such as oil leaks, engine deposits, and sludge formation. On top of that, the wrong oil in newer engines may void their warranty and put your engine at risk of eventual engine damage.
2. Can You Mix 5W-20 And 5W-30 Oils?
While some engines may allow it, most mechanics will advise you against mixing two multigrade oils. In some cases, using the wrong oil or mixing two different oils can void your car’s warranty and cost you a fortune in repairs.
You’re also risking your engine life and weakening the internal combustion engine’s durability.
Mixing 5W-20 and 5W-30 (or any other oils for that matter) may lead to faster wear and tear of your engine and eventually cause problems with the basic functioning of critical engine parts.
And even if your engine allows it, you won’t get any noticeable results by mixing different viscosity grade oils. So even if your car engine is versatile in terms of the oil viscosity grade it uses, it’s best to stick to a single viscosity rating at a time.
3. Are 5W-20 And 5W-30 Oil Synthetic?
Both 5W-20 and 5W-30 oils are available in conventional and synthetic oil variants.
Conventional oil is made using refined crude oil as a base oil, along with various additives (like a viscosity index improver or corrosion inhibitor). It provides decent fuel economy, protection against friction, and damage to various engine parts.
However, conventional oil doesn’t last as long as synthetic oil.
Synthetic motor oil, on the other hand, is very reliable and highly stable in extreme temperatures. In fact, a 5W-20 synthetic oil may perform even better in warmer temperatures than 5W-30 conventional oil. This is because synthetic motor oil is made by breaking down and rebuilding hydrocarbon atoms for a more stable operating temperature range.
5W-20 and 5W-30 oils are also available as synthetic blend variants. Synthetic blend multi-grade oil will perform better than regular oil and be cheaper than the synthetic oil type.
NOTE: Older or high-mileage engines may require a special high-mileage oil to properly protect the engine. High-mileage vehicles are those that have more than 75,000 miles on them.
If your car falls under this category, consult your car mechanic for the right kind of high mileage oil for your car (5W-20 or 5W-30).
4. What Happens If You Use The Wrong Oil In Your Car?
If you accidentally used the wrong oil for your engine, the first thing to do is drain out your oil and get an oil change. While it may not cause any immediate damage to your engine’s life, it’s best not to risk it.
If you’re on the road with no means to replace your oil, follow these instructions:
- Drive slowly and monitor your speed.
- Keep an eye on the engine’s temperature limit, and do not let your engine reach a hotter temperature.
- If the normal operating temperature does reach the ‘red’ zone, pull over and turn off the engine. Wait for some time before you start driving again to cool down the engine.
- If the engine keeps getting hot, reach out to roadside assistance for help.
Keep in mind that you should always keep a close eye on the type of oil you use in your engine. If your mechanic accidentally refills the wrong oil, let them know and get an oil change. Otherwise, you may run into problems like unusual engine noise, oil leaks, and engine deposits. You may also detect a burning smell from the engine, reduced fuel efficiency, and increased oil consumption.
Skip the Confusion — Book a Professional Oil Change Today
When choosing between 5W20 and 5W30 oil, your vehicle manufacturer’s manual should tell you everything you need to know. And if it doesn’t, reach out to your car mechanic to find the viscosity grade best suited to your car.
However, regardless of which oil you choose, remember to follow regular maintenance and oil change routines for a healthy engine.
And if you need any help with your car’s maintenance and repair, oil-related or otherwise, reach out to AutoNation Mobile Service!
We are a mobile car maintenance and repair service offering competitive, upfront pricing for a range of car-related solutions.
Contact us to have expert mechanics at your driveway!