5W20 and 5W50 may look similar on the shelf, but their impact on fuel efficiency, engine wear, and daily driving is anything but the same. Need guidance? Call us at 1(866) 511-0898.
Key difference between 5W 20 and 5W 50
- 5W20: Thinner, fuel-efficient, best for modern, light-duty engines, quick cold starts.
- 5W50: Thicker, high-performance protection, ideal for turbocharged, heavy-duty, or extreme-temperature engines.
- Rapidwrench is ready to help you pick the right oil and provide professional mobile mechanic service anywhere in the United States. Call 1(866) 511-0898 for expert guidance.
| Attribute | 5W20 | 5W50 |
|---|---|---|
| Density @ 15°C | 0.852 kg/L – Lightweight, improves pump efficiency | 0.85–0.86 kg/L – Slightly heavier for high-pressure protection |
| Viscosity @ 40°C | 51.9 cSt – Flows easily for daily commuting | ~110–130 cSt – Maintains thickness under heavy loads |
| Viscosity @ 100°C | 8.7 cSt – Optimized for fuel efficiency | 18–20 cSt – Superior protection in extreme conditions |
| Viscosity Index | 145 – Stable for moderate driving conditions | ~180 – Exceptional stability at high temperatures and stress |
| Pour Point | -42°C – Excellent cold start performance | -36 to -42°C – Slightly less ideal for extreme cold, better for high-heat scenarios |
| Flash Point | 224°C – High safety margin for normal engine operation | >224°C – Increased thermal protection under heavy usage |
| Fuel Efficiency Impact | +1–2% improvement – Reduces internal friction | -1–2% – Slightly higher fuel consumption due to viscous drag |
| Engine Compatibility | Gasoline, light-duty, modern engines – Daily driving, moderate loads | Turbocharged, performance, heavy-duty engines – High stress, racing, towing |
| Optimal Temperature Range | -42°C to ~100°C – Ideal for moderate climates and standard conditions | -36°C to 140°C+ – Best for high-temperature, high-stress environments |
| Practical Usage Scenarios | Commuting, fuel-conscious driving, moderate city traffic | Performance driving, towing, racing, extreme heat or high RPM use |
| Engine Wear Protection | Good for normal driving – Reduces friction-related wear | Excellent under high stress – Maintains protective film at elevated temperatures |
| Cold Start Performance | Quick flow – Rapid lubrication at startup | Good, but slightly slower flow in small engines compared to 5W20 |
1. Viscosity Differences: Thinner vs. Thicker Oils
The 5W20 oil flows more easily at operating temperatures, measuring around 8.7 cSt at 100°C, which helps smaller engines run efficiently. On the other hand, 5W50 is much thicker at 18-20 cSt at 100°C, designed for high-performance engines that need a stronger protective film under heat and stress. This difference directly affects how your engine handles wear and fuel efficiency.
2. Engine Protection: Everyday Driving vs. High-Performance
Because 5W50 maintains higher viscosity at elevated temperatures, it provides better protection in turbocharged or heavy-duty engines. Conversely, 5W20 is tailored for modern gasoline engines where thinner oil reduces friction, saving 1-2% on fuel consumption under normal driving conditions.
3. Cold Start Performance: Quick Flow Matters
The “5W” rating means both oils perform well in cold starts. However, the lower hot-temperature viscosity of 5W20 ensures quicker circulation immediately after ignition, crucial in cold climates. 5W50, while still starting well in the cold, takes slightly longer to circulate fully in smaller engines.
4. Density and Flow Characteristics
At 15°C, 5W20 has a density of 0.852 kg/L, making it slightly lighter than 5W50, which generally ranges from 0.85 to 0.86 kg/L. This subtle difference influences pump efficiency, engine lubrication speed, and overall performance in daily driving.
5. Fuel Efficiency: Small Gains vs. Engine Stress Tolerance
Because 5W20 is thinner at operating temperature, engines can run with lower internal friction, improving fuel economy. 5W50, by contrast, slightly reduces fuel efficiency because of higher viscous drag, but it compensates by offering superior protection in high-temperature or heavy-load scenarios.
6. Engine Compatibility: Light-Duty vs. High-Duty Applications
5W20 fits most passenger cars and light-duty gasoline engines, making it ideal for fuel-conscious drivers. 5W50 shines in performance cars, racing vehicles, and heavy-duty trucks, where high stress, heat, and turbocharging demand extra viscosity for protection.
7. Viscosity Index: Stability Across Temperatures
With a viscosity index of 145, 5W20 performs consistently in moderate conditions. In contrast, 5W50 often has a viscosity index around 180, meaning it maintains thickness better at high temperatures—a critical factor for engines running in extreme heat or high RPM conditions.
8. Pour Point and Extreme Conditions
The pour point of 5W20 is -42°C, which makes it excellent for cold starts. 5W50 usually ranges between -36 to -42°C, offering slightly less cold weather performance but unmatched thermal protection in extreme heat, heavy towing, or racing conditions.
9. Flash Point and Safety
Both oils boast high flash points: 5W20 at 224°C and 5W50 slightly higher. This attribute is essential for avoiding oil breakdown under high temperatures, which is especially important in engines running hard for extended periods.
10. Cost Comparison: 5W 20 vs 5W 50
Because 5W50 uses more base oils and additives to achieve higher viscosity and thermal protection, it usually costs more. For example, a 1-quart bottle of 5W20 typically retails around \$6–\$8, whereas 5W50 can range from \$10–\$14 per quart, depending on brand and formulation. This price difference makes 5W20 more economical for standard daily driving, while 5W50 justifies the cost for high-performance, heavy-duty, or extreme-condition engines.
Final thoughts
Now you know the difference between both 5W 20 and 5W 50! If you want to avail any services feel free to contact Rapidwrench mobile mechanics in United States
Additional resources
Frequently Asked Questions
What is the main difference between 5W20 and 5W50 motor oil?
The main difference is viscosity at operating temperature. 5W20 is thinner (8.7 cSt at 100°C) and improves fuel efficiency, while 5W50 is thicker (18-20 cSt at 100°C) and offers superior protection in high-performance or high-temperature engines.
Can I use 5W50 instead of 5W20 in my car?
You can in some cases, but it depends on the manufacturer’s recommendations. Thicker oil like 5W50 may reduce fuel economy and slightly affect engine performance in light-duty, fuel-efficient vehicles. Rapidwrench advises checking your engine specifications first.
Are 5W20 and 5W45 similar?
They are similar in cold-start behavior (both 5W), but 5W45 is thicker at high temperatures than 5W20, offering better engine protection in hotter conditions or high-performance applications.
How does cold weather affect 5W20 vs 5W50?
Both oils have a “5W” winter rating, allowing cold start flow. 5W20 circulates slightly faster in smaller engines, which is advantageous in extremely cold climates, while 5W50 still provides adequate cold-start protection but favors high-heat stability over flow speed.
Does 5W50 perform better in summer than 5W20?
Yes. While both oils work year-round, 5W50 maintains thicker protection under high-temperature summer conditions, making it better suited for hot climates or high-stress driving.
How often should I change 5W20 vs 5W50?
Change intervals depend on the manufacturer’s recommendation, but generally, 5W20 is changed every 5,000-7,500 miles, while 5W50 may extend slightly in heavy-duty or synthetic formulations. Always verify with your vehicle manual.
Can I mix 5W20 and 5W50 in an emergency?
Mixing is not recommended. Temporary topping up may be acceptable, but long-term mixing can compromise viscosity balance and protection, leading to engine wear.
Can switching from 5W20 to 5W50 improve engine life?
For high-performance or heavily loaded engines, yes. The thicker oil offers better protection against heat and wear, but for light-duty engines, it may reduce fuel efficiency without significant longevity benefits.
What factors should I consider when choosing between 5W20 and 5W50?
Consider engine type, driving style, climate, fuel efficiency priorities, and manufacturer specifications. Rapidwrench emphasizes evaluating these factors carefully to select the oil that balances performance, protection, and economy.