Difference Between 5W-30 And 10W-30. Which Is Better? - ÖleZol

5W-30 VS 10W-30

5W-30 and 10W-30 oils perform similarly when the engine is running, typically at around 212°F (100°C). At this operating temperature, there is almost no difference between the two oils. However, the distinction lies in their viscosity characteristics at lower temperatures. 10W-30 oil is thicker when the engine is cold, which can affect its flow properties during startup and initial engine warm-up.API (American Petroleum Institute) guidelines suggest using 10W–30 oil if you expect the outside temperature to stay above 0°F (-18°C). In regions where temperatures frequently drop below this threshold, it’s recommended to use 5W–30 oil. This ensures proper lubrication and protection for the engine, especially during cold starts when most engine wear occurs.

5W–30 vs 10W–30 when the engine is running:

Engine oil viscosity indicates how easily the oil flows at different temperatures, ensuring proper lubrication and protection for the engine’s components. Shown in the video are 5W–30 and 10W–30 engine oils in tubes at 100°C (212°F). A steel ball moving from top to bottom indicates the thickness or viscosity of the oil. At 100°C (212°F), the viscosity or resistance to flow is almost the same for both 5W–30 and 10W–30.

The number 30 in both 5W-30 and 10W-30 indicates the SAE viscosity at 100°C (212°F). That is the operating temperature of an average engine. The number before “W” (5W-XX and 10W-XX) tells the SAE viscosity of the oil when it is cold. W indicates winter or cold and that’s why it is shown here in blue color.

In the example above, 5W-30 has “SAE 5” viscosity and 10W-30 has “SAE 10” viscosity (5W and 10W) when cool. A higher SAE number means that the oil is thicker or has a high viscosity. SAE 10 is thicker than SAE 5, and similarly, SAE 40 is thicker than or has a higher viscosity than SAE 30. Check the SAE Viscosity chart called SAE J300 standard.

So both the oils 5W–30 and 10W–30 have the same viscosity (SAE 30) when your engine is running, and will perform in the same way. However, the 10W–30 oil will be thicker (higher viscosity) than the 5W–30 when it is cool.

“W” relates to winter or cold

Shown in the video are tubes with 5W-30 and 10W-30 lubricants. Both tubes with the steel ball were refrigerated at -18°C for half an hour. Air bubbles are trapped in the test tubes because of the low temperature. The thickness of 10W-30 is much higher, as shown in the video demonstration.

Which is better?

In modern car engines, it’s important for the oil to have good flow characteristics at startup, which means it needs to be thinner. During startup, when the engine is cold, the oil needs to quickly reach all critical engine components to provide lubrication and reduce wear. It’s widely acknowledged that a significant portion, often estimated around 80%, of engine wear occurs during startup, particularly during the warming-up phase when engine components are not yet at their optimal operating temperatures. 5W–30 oil has the same viscosity at 100°C but is thinner when cool. 5W–30 is usually a semi-synthetic or fully synthetic lubricant. The only problem with 5W–30 is NOACK (evaporation tendencies of a lubricant (engine oil) at high temperature).

Conclusion:

In colder climates, 5W-30 is preferred because its better cold-start performance helps reduce engine wear. In milder regions where temperatures rarely drop below freezing, 10W-30 provides similar protection and works just as effectively. Since both have the same viscosity at operating temperature, the choice mainly depends on climate conditions and the manufacturer’s recommendations.

According to the API motor oil guide [1], if you are using 10W-30 you can safely switch to 5W-30 in most car engines. 5W-30 flows more easily when cold, while both have the same viscosity once the engine is at operating temperature. However, switching from 5W-30 to 10W-30 is not always recommended, unless the lowest expected outdoor temperature stays above –18 °C (0 °F). Always follow the manufacturer’s recommendations.

For example, in my car I use synthetic 5W-40 instead of 15W-40. Both grades are approved by the manufacturer, even in the hot Gulf climate. The 5W-40 version is synthetic, offering better oxidation resistance and longer drain intervals compared to mineral-based 15W-40.

Can I use 10W-30 instead of 5W-30?

Always follow your engine manufacturer’s recommendations. Both 5W-30 and 10W-30 have the same viscosity at operating temperature, but 5W-30 flows better in cold starts, making it more versatile for a wider range of climates. You can use 10W-30 if your climate rarely drops below –18 °C (0 °F). Both grades are available in synthetic and mineral forms, though synthetic is generally preferred for better performance and protection.

Can you use 5W-30 instead of 10W-30?

Both 5W-30 and 10W-30 have the same viscosity at normal engine operating temperature. The main difference is in cold starts: 5W-30 flows better in colder weather, which reduces wear during startup. This makes it more versatile across a wider range of climates. For high-performance or diesel engines, always follow the manufacturer’s recommended oil grade and specification.

Is 10W-30 thicker than 5W-30?

Both 5W-30 and 10W-30 have the same viscosity at normal engine operating temperature (about 100 °C / 212 °F). The difference is at cold start: 10W-30 is thicker than 5W-30 when the oil is cold, while 5W-30 flows more easily in lower temperatures.

What does the “W” stand for in the SAE viscosity grades?

“W” stands for winter, for example in 5W–30, the lubricant has SAE 5 viscosity when cold and SAE 30 viscosity when the engine is running. There are 2 sets of numbers in 5W–30 separated by a dash(-). The number 30 [3] relates to the viscosity or thickness of the oil when it is at 100°C. It is considered a working temperature for the average engine. The “W” means winter and 5W relates to how the oil performs when it is cool. So 5W–30 is SAE 30 viscosity when at 100°C and SAE 5 viscosity when cool.

References:

(1) Motor Oil Matters by api.org

(2) SAE Viscosity Grades.

(3) SAE J3oo viscosity grades for engine oil