What is the difference between 5W 20 oil and 5W-30 oil?
Both 5W-20 and 5W-30 are common multi-grade oils, but they behave differently under engine heat. In general, 5W-30 is thicker at operating temperature, offering stronger film protection, while 5W-20 is thinner and often chosen to support better fuel economy. Always follow the vehicle manufacturer’s specification for your engine.
What the numbers mean
The numbers indicate viscosity characteristics. The first number before the W (5) measures cold-start viscosity: a lower number means the oil flows more easily when the engine is cold. The second number after the W (20 or 30) measures viscosity at 100°C when the engine is hot. Since both oils have a 5W cold rating, their cold-start performance is similar, but the higher 30 weight in 5W-30 means a thicker oil film once the engine warms up. The exact protection also depends on the oil’s base stock and additives.
Why the difference matters
In practice, the hot-viscosity difference translates into how thick the oil film remains under heat and load. This can influence wear protection, oil consumption, and fuel efficiency depending on the engine and driving conditions.
Viscosity profiles and protection
Before a side-by-side look, note how each grade behaves as temperatures rise or fall and under different engine loads.
- Cold-start and startup wear: Both grades share the same 5W winter rating, so lubrication onset during cold starts is similar in typical climates.
- Hot-temperature film strength: 5W-30 maintains a higher viscosity at engine temperatures, offering a thicker lubricating film under heat and stress than 5W-20.
- Engine load and longevity: Engines designed for 5W-30 typically benefit from the extra film thickness in hot or high-load situations; engines designed for 5W-20 rely on the lower hot-viscosity grade for efficiency and adequate protection as specified by the manufacturer.
In short, 5W-30 provides stronger protection at hotter operating conditions, while 5W-20 supports lower friction and improved efficiency when the engine is operating within its designed specifications.
Practical considerations for choosing
Guidance to help decide which grade to use in a given vehicle and climate:
- Follow the manufacturer’s specification in the owner’s manual or on the oil cap. The approved grade balances wear protection, fuel economy, and engine tolerances.
- Consider climate and driving style: hot climates or engines carrying heavy loads may benefit from 5W-30, while mild climates and routine city driving may be well served by 5W-20.
- Check warranty and service history: some warranties require a specific viscosity; mixing grades or using the wrong grade can affect coverage and performance.
Always verify with a dealer or mechanic if you’re unsure, and avoid mixing grades unless explicitly advised by the manufacturer or a qualified technician, as it can disrupt the oil’s protective balance.
Summary
The core difference is how thick the oil remains at engine operating temperature. 5W-30 is thicker at hot temperatures, offering stronger film protection in hotter or high-load conditions, while 5W-20 stays thinner to reduce friction and improve efficiency in engines designed for that specification. Both share the same cold-start performance, but the right choice depends on your vehicle’s official specification, climate, and typical driving conditions. Always consult the owner’s manual for the correct grade.
Is 5W20 good for high mileage?
Yes, 5W-20 is good for high-mileage engines, especially if the vehicle's manufacturer recommends it, as it provides better fuel efficiency and protection against wear. High-mileage 5W-20 oils are specifically formulated with additives to help with issues common in older engines, such as reducing leaks and cleaning sludge.
Benefits of using 5W-20 high-mileage oil
- Improved engine protection: High-mileage oils contain additives that help protect worn seals and prevent leaks.
- Reduces sludge: These oils are formulated to help reduce the buildup of sludge in the engine.
- Long-lasting protection: They provide long-lasting protection to help extend the engine's life.
- Optimal viscosity: 5W-20 flows easily, which helps with cold starts and can lead to better gas mileage compared to thicker oils like 5W-30.
Important considerations
- Check your owner's manual: Always follow the viscosity recommended in your vehicle's owner's manual. Using the wrong viscosity can lead to engine damage.
- Understand the "high mileage" claim: High-mileage oils are designed for engines with over 75,000 miles, but can also be beneficial for older vehicles showing signs of engine wear.
- Consider the type of oil: 5W-20 can be mineral, semi-synthetic, or full synthetic, each with a different lifespan. For high-mileage engines, a full synthetic or high-mileage blend is often recommended for better performance and protection, notes Quora users.
Can you mix 5W20 and 5W30?
While you can technically mix 5W-20 and 5W-30, it is not recommended because it can alter the intended oil viscosity for your engine, potentially leading to reduced performance or engine wear. It's best to use the single oil grade recommended in your vehicle's owner's manual to ensure proper lubrication and protect the engine's components.
You can watch this video to learn about the implications of mixing 5W20 and 5W30 oils: 42sMotor MatchupsYouTube · Jan 6, 2024
Why you should avoid mixing oils
- Alters viscosity: Mixing them creates an oil with a viscosity somewhere between 5W-20 and 5W-30, which may not be ideal for your engine's operating conditions.
- Potential for engine wear: Using a mix can lead to higher engine wear or other issues because the engine's components were designed for a specific oil viscosity.
- Impact on performance: An incorrect viscosity can lead to a slight decrease in fuel mileage or could potentially strain the oil pump.
- Unpredictable additive interactions: Mixing different brands can also alter the balance of the carefully formulated chemical additives, as each brand uses its own proprietary formula.
What to do if you've mixed them
- If you have accidentally mixed a small amount of 5W-30 into a 5W-20 (or vice versa) engine, you are unlikely to cause immediate, catastrophic damage, especially if your vehicle is not a high-performance or hybrid model.
- It's best to check your owner's manual to see what the recommended oil is and then take steps to correct the oil mixture.
- The safest course of action is to have the oil changed to the correct weight as soon as possible to prevent any long-term issues.
Is 5W-30 oil good for hot weather?
The conversation revolves around the suitability of using 5w30 oil in a vehicle, with various opinions and experiences shared by the participants, including the consideration of weather conditions and warranty implications. Absolutely. 5w30 is actually recommended in hot weather areas.
Does it matter if you use 5W-20 or 5W-30?
Yes, there is a significant difference: 5W-30 is thicker than 5W-20 at high temperatures, which can offer better protection in demanding conditions, while the thinner 5W-20 can provide slightly better fuel economy and easier cold starts. The key difference is the "30" versus the "20" at the end of the name, indicating viscosity once the engine is warm. Always check your vehicle's owner's manual for the manufacturer's specific recommendation.
Key differences
| Feature | 5W-20 | 5W-30 |
|---|---|---|
| High-temperature viscosity | Thinner | Thicker |
| Engine protection | Less protection under heavy loads; better for modern engines with tighter tolerances | Better protection at high temperatures and under heavy use, like towing |
| Fuel efficiency | Higher | Lower |
| Cold weather starts | Slightly easier starts due to lower viscosity | Both are designed for cold starts since the "5W" is the same, but the 5W-20 will have slightly less resistance when cold |
| Best for | Newer vehicles, city driving, fuel efficiency | Older vehicles, towing, heavy loads, hot climates |
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What to do
- Consult your owner's manual: This is the most important step, as the manufacturer specifies the correct oil for your engine's design and performance.
- Consider your climate and driving habits:
- If you live in a cold climate and do mostly short trips, 5W-20 might be ideal.
- If you frequently tow, drive in hot weather, or put many miles on your car, 5W-30 offers better protection.
- Understand the trade-off: Using the thicker 5W-30 in an engine designed for 5W-20 may slightly decrease fuel economy and potentially lower long-term engine life, while using the thinner 5W-20 in an engine designed for 5W-30 may lead to more wear over time.
