0W-40 vs 5W-30: Which Engine Oil Is Better?

Neither 0W-40 nor 5W-30 is universally “better” — the right choice depends on your car manufacturer’s specification, your climate, and how you drive. In cold climates or for high-performance engines that experience a wide temperature range, 0W-40 often offers an advantage, while 5W-30 is typically better suited to moderate climates and everyday driving when it matches the factory recommendation.

Understanding What 0W-40 and 5W-30 Actually Mean

Both 0W-40 and 5W-30 are multigrade engine oils, but their numbers reflect different flow characteristics at different temperatures, as defined by SAE (Society of Automotive Engineers) viscosity standards. Knowing what those numbers mean is key to deciding which oil is appropriate for your vehicle.

The Viscosity Numbers Explained

The designations “0W-40” and “5W-30” each contain two numbers separated by the letter “W,” which stands for “winter.” These numbers describe how thick or thin the oil is at cold start and at normal operating temperature, which directly affects engine protection and efficiency.

The following list explains each part of the oil grade and how it affects performance.

• First number (0W vs 5W): Indicates low-temperature viscosity. A 0W oil flows more easily than a 5W oil at very low temperatures, improving cold starts and early engine protection.
• Letter “W”: Stands for “winter,” confirming the first number is a cold-weather viscosity rating, not weight.
• Second number (40 vs 30): Indicates viscosity at operating temperature (around 100°C / 212°F in testing). A 40-weight oil is thicker than a 30-weight oil when hot, generally offering a stronger film but slightly more drag.
• Multigrade behavior: Both oils behave thinner when cold and thicker when hot compared with a single-grade oil, helping engines cope with wide temperature swings.

Together, these figures describe how oil will behave from cold start to full operating temperature, allowing engineers and drivers to match oil characteristics to engine design and conditions.

Key Differences Between 0W-40 and 5W-30

While both oils can protect modern engines, they are optimized for different use cases. Their differences show up most clearly at very low temperatures and under high-heat, high-load conditions.

Cold-Start Performance

Cold-start lubrication is one of the most critical aspects of engine protection, as most wear happens in the first seconds after starting the engine.

This list highlights how each grade behaves in cold conditions.

• 0W-40: Flows better than 5W-30 in very cold weather, reducing starter strain and helping oil reach critical components faster. Typically recommended for colder climates (e.g., sustained temperatures below -20°C / -4°F) or where manufacturers specify 0W grades.
• 5W-30: Still provides good cold-start performance, suitable for mild to moderately cold climates. In regions where winter temperatures rarely drop well below freezing, 5W-30 is usually adequate and widely recommended.
• Real-world impact: In extremely cold climates (northern U.S., Canada, Scandinavia, parts of Eastern Europe), the 0W advantage can be noticeable in quicker starts and smoother early running.

In essence, 0W-40 has an edge in extreme cold, but for most temperate environments, 5W-30 is usually sufficient if that’s what the manufacturer recommends.

High-Temperature and High-Load Protection

Once the engine warms up, the second number in the viscosity rating comes into play, particularly during sustained highway driving, towing, or performance use.

The following points summarize hot-temperature performance differences.

• 0W-40 (40-weight when hot): Thicker film at operating temperature than 5W-30, which can provide extra protection under high load, high RPM, or track use. Many European performance and turbocharged engines specify 0W-40 or similar (e.g., 5W-40).
• 5W-30 (30-weight when hot): Slightly thinner at operating temperature, often favored for fuel efficiency and emissions. Commonly specified for modern everyday cars, especially in North America and Asia, because it balances protection, economy, and emissions control.
• Thermal stability: High-quality 0W-40 synthetics often carry strong approvals (e.g., Mercedes-Benz, BMW, Porsche, VW, ACEA A3/B4), signaling robust performance under demanding conditions. Many 5W-30 oils focus on long-drain intervals and fuel-economy standards (e.g., ILSAC GF-6, API SP).

The thicker hot viscosity of 0W-40 can be advantageous in hard use, but for everyday commuting and moderate driving, 5W-30 typically offers more than enough protection with a slight fuel-economy advantage.

Fuel Economy and Emissions

Automakers increasingly tune their oil recommendations to help meet fuel-economy and emissions regulations, which is why lighter oils have become more common.

The points below outline efficiency considerations for both grades.

• 5W-30: Generally offers marginally better fuel economy due to lower internal friction at operating temperature. Many modern gasoline engines are calibrated and tested on 5W-30, and some 5W-30 oils are specifically labeled as “fuel economy” or “resource conserving.”
• 0W-40: Slightly thicker at temperature, which can reduce fuel economy by a small amount. The difference is usually modest but can matter over time in fleets or for manufacturers managing regulatory targets.
• Regulatory context: In the U.S. and many other markets, factory recommendations are tightly linked to official fuel-consumption and emissions testing, which is one reason 5W-30 and even 0W-20 are so widely specified.

While the fuel-economy edge of 5W-30 is real, for most individual drivers it is small; manufacturer approval and climate usually matter more than minor MPG differences.

What Automakers and Standards Actually Recommend

The most important factor in choosing between 0W-40 and 5W-30 is whether the oil meets the specifications listed in your owner’s manual. Modern engines are designed around specific viscosity ranges and performance standards.

Manufacturer Specifications and Approvals

Beyond viscosity, oils carry industry and manufacturer approvals that indicate they have passed tests for wear protection, deposit control, compatibility with emissions systems, and more.

This list outlines what to look for when comparing oils.

• Owner’s manual first: Always check the viscosity range and the performance standards (API, ILSAC, ACEA, and OEM specs like VW 502.00, MB 229.5, BMW LL-01, GM dexos, etc.).
• European cars: Many European gasoline and diesel engines, especially turbocharged models from Mercedes-Benz, BMW, Audi, Porsche, and VW, traditionally approve 0W-40 or 5W-40 oils that meet ACEA A3/B4 and specific OEM standards.
• North American & Asian cars: Many Toyota, Honda, Ford, GM, Hyundai, and similar brands frequently specify 5W-30 or even lighter grades (0W-20, 5W-20) that meet ILSAC GF-6 / API SP and their own in-house standards.
• Warranty implications: Regularly using an oil grade or specification outside the manufacturer’s requirements can risk warranty coverage, especially on newer vehicles.

Matching the specification and viscosity range recommended by your manufacturer is the safest and most reliable way to choose between 0W-40 and 5W-30.

Climate, Driving Style, and Engine Type

Even within the bounds of manufacturer recommendations, climate and usage can tilt the choice toward one viscosity grade or another, particularly in regions with extreme temperatures.

Climate Considerations

Oil must remain fluid in cold weather yet robust in high heat. Your local environment plays a major role in which oil performs best day to day.

The following points summarize how climate influences the decision.

• Very cold climates: If winter temperatures routinely drop below -20°C (-4°F), 0W-40 can provide faster lubrication at startup than 5W-30, if it is approved by your manufacturer. Some manuals explicitly list both 0W and 5W options depending on temperature ranges.
• Moderate climates: In areas where winters are mild and summers warm (typical of much of Europe, the U.S., and Asia), 5W-30 is commonly used and works well when recommended for the engine.
• Very hot or mountainous regions: In consistently hot climates or where engines are regularly under heavy load (e.g., long hill climbs, towing), a 40-weight oil such as 0W-40 can deliver a thicker film at operating temperature, again assuming the engine is approved for that grade.

Choosing an oil that aligns with both your local temperature range and the manufacturer’s viscosity chart is crucial for long-term engine health.

Driving Style and Engine Design

How and where you drive, along with whether your engine is naturally aspirated or turbocharged, can also influence which oil is more suitable.

These examples illustrate when each oil might be preferred, provided it meets the required specifications.

• High-performance or turbocharged engines: Many performance-focused or turbo engines—especially European models—are factory-approved for 0W-40 due to its stronger high-temperature film strength.
• Daily commuting and light-duty use: For typical city and highway driving in a mainstream sedan or compact SUV, 5W-30 is very often the default recommendation, balancing protection and efficiency.
• Towing and heavy loads: In vehicles frequently towing or carrying heavy loads in hot conditions, a 40-weight oil (0W-40 or 5W-40 as specified) can offer an extra margin of protection.
• Older, high-mileage engines: Some owners of older cars with looser internal clearances may prefer a slightly thicker hot viscosity, but any change should still be within the range allowed by the manufacturer’s manual.

Ultimately, your engine’s design and your real-world usage should guide the choice, with the owner’s manual setting the hard boundaries.

Cost, Availability, and Brand Considerations

In many markets, 5W-30 is the most widely available grade, but high-quality 0W-40 synthetics are also easy to find, especially in regions with many European cars or performance enthusiasts.

Practical Factors at the Parts Store

Beyond performance, drivers often weigh cost, convenience, and brand reputation when picking an oil off the shelf.

This list covers practical differences between buying 0W-40 and 5W-30.

• Availability: 5W-30 is one of the most common viscosities worldwide and is usually available in basic conventional, synthetic-blend, and full-synthetic versions. 0W-40 is more likely to be found as a premium full-synthetic product.
• Price: 0W-40 full-synthetics are often slightly more expensive per liter than mainstream 5W-30 oils, though price gaps have narrowed as synthetics become standard.
• Brand and approvals: High-profile 0W-40 oils (for example, those carrying multiple European OEM approvals) are popular choices for performance cars. For 5W-30, it’s important to check the label for the correct API/ILSAC and OEM approvals rather than relying on viscosity alone.

While price and availability matter, they should not override the need to match your vehicle’s specification; the cost of incorrect oil can easily outweigh small savings at purchase time.

So, Which Is Better: 0W-40 or 5W-30?

The debate often appears in forums and among enthusiasts, but the answer hinges on your specific vehicle and conditions rather than a one-size-fits-all verdict.

The following points summarize when each oil typically makes the most sense, assuming both grades are approved by your manufacturer.

• 0W-40 is generally preferable if:
  

  • You live in a region with very cold winters and need excellent cold-start performance.
  • You drive a performance-oriented or turbocharged engine that lists 0W-40 among its approved viscosities.
  • Your vehicle sees high-stress use—spirited driving, track days, or frequent heavy loads—where a 40-weight hot viscosity offers extra protection.

• 5W-30 is generally preferable if:
  

  • Your owner’s manual specifically calls for 5W-30 as the primary or only recommended grade.
  • You drive mostly under normal conditions in a moderate climate, focusing on reliability, fuel economy, and emissions compliance.
  • You want a widely available, cost-effective oil grade that matches typical modern gasoline engine requirements.

• When in doubt: Follow the owner’s manual exactly, including viscosity and approval standards; if multiple viscosities are allowed, then choose based on climate and driving style.

Rather than asking which grade is absolutely better, the more accurate question is which one is better for your specific engine, climate, and usage pattern within the boundaries set by the manufacturer.

Summary

0W-40 and 5W-30 are both modern multigrade oils designed to protect engines across a range of temperatures. 0W-40 flows more easily in extreme cold and maintains a thicker film at high operating temperatures, making it a strong option for cold climates and performance or high-load applications—provided your engine is approved for it. 5W-30, on the other hand, is widely recommended for everyday vehicles, especially in moderate climates, offering a good balance of protection, fuel economy, and emissions compatibility. The decisive factor is not which grade is “better” in abstract, but which one matches your owner’s manual specifications, your local climate, and the way you actually drive.