Yes. In cold conditions, 5W-20 is generally thicker than 0W-20, but both oils are designed to have the same viscosity rating of about 20 cSt at 100°C when the engine is hot. The practical difference shows up mainly at startup in cold weather.
What the numbers mean
The two-number system on engine oils uses the first number with a W to indicate cold-weather viscosity, while the second number (20 in both cases) represents viscosity at engine operating temperature (roughly 100°C). A lower first-number (0W vs 5W) means the oil will be thinner and flow more easily during cold starts, helping lubrication right after a cold start. The hot-temperature viscosity is intended to be similar for both grades, typically around 20 cSt at 100°C, though exact values can vary by formulation and brand.
Cold-start thickness comparison
Here's how these two grades typically compare in cold conditions:
- 0W-20 flows more readily at cold temperatures, providing quicker lubrication on startup in very cold climates.
- 5W-20 is thicker than 0W-20 at cold temperatures, offering a slightly higher resistance to flow right after starting the engine.
- Both oils are designed to meet a similar high-temperature viscosity target (around 20 cSt at 100°C), supporting protection once the engine warms up.
- Actual viscosity can vary by brand and formulation; some modern synthetic 5W-20 blends may come very close to 0W-20 in practice.
In practice, the cold-start thickness difference matters most in very cold climates or extreme starting conditions. For everyday driving in moderate climates, the difference is typically modest, and you should follow the vehicle manufacturer’s specification.
Hot operating temperature and manufacturer guidance
At engine operating temperature, the two grades are engineered to behave similarly, with the second number indicating the target viscosity at 100°C. Manufacturers may approve multiple grades (such as 0W-20 and 5W-20) for a given engine to accommodate climate or warranty considerations. Always consult the owner's manual or the manufacturer's oil specification for your specific vehicle, as engine tolerances and fuel-economy targets can influence the recommended grade.
Practical takeaways for drivers
When choosing between 0W-20 and 5W-20, keep these considerations in mind:
- If you live in very cold climates, 0W-20 is generally easier to start and protects moving parts sooner after startup.
- In milder climates or under heavier startup wear scenarios, 5W-20 can be a suitable alternative that still meets the same hot-temperature specification.
- Most modern engines are compatible with either grade as long as the oil meets the manufacturer’s spec and viscosity requirements.
- Always verify the exact specification in your owner's manual or with your vehicle’s manufacturer, especially for warranties or updated engine designs.
The key takeaway is to follow the recommended grade for your vehicle and climate. The cold-start difference is the main practical distinction between 0W-20 and 5W-20, while the hot-temperature performance is designed to be comparable.
Summary
In short, 0W-20 is typically thinner than 5W-20 at cold temperatures, aiding rapid lubrication during startup. Both grades aim for a similar hot-viscosity target around 20 cSt at 100°C, so their performance in warm running conditions is often comparable. The best choice depends on the vehicle manufacturer’s specification and your climate, with the manual providing the authoritative guidance.
What are the disadvantages of 0W-20 engine oil?
Conversely, engines designed for 5W30 but using 0W20 may develop bearing knock, excessive oil consumption, and accelerated wear. Monitor these symptoms and switch to proper viscosity if they appear.
What is thinner, 0W-20 or 5W20?
Both 0W-20 and 5W-20 have similar viscosity at operating temps, with 0W-20 being slightly thinner. The lower viscosity of 0W-20 can provide better fuel economy compared to 5W-20 due to reduced friction and drag on the engine. 0W-20 oils require synthetic base oils and are not conventional oils.
What if you use 5W20 instead of 0W-20?
In hot climates, both 0W-20 and 5W-20 provide identical protection since they share the same high-temperature viscosity (SAE 20). The "0W" vs "5W" designation only affects cold-temperature performance below 70°F.
Is 0W-20 destroying engines?
Scientific testing conclusively demonstrates that 0W-20 oil, when properly specified and maintained, extends engine life by 45%, reduces wear by 60%, and improves fuel economy by 6-8% compared to thicker oils in engines designed for this viscosity grade.