The numbers you mentioned, such as 5W-30 and 10W-30, are viscosity ratings for engine oil. They indicate the oil's viscosity or thickness at different temperatures.
The "W" stands for winter, and the number preceding it represents the oil's viscosity at low temperatures, while the number after the hyphen represents the viscosity at high temperatures.
In the case of 5W-30 oil, it means that the oil has a low-temperature viscosity equivalent to that of a 5-weight oil, which flows more easily in colder conditions. This allows for easier starting and better lubrication during cold starts. The high-temperature viscosity, indicated by the second number (30), is thicker than the low-temperature viscosity. This helps maintain proper lubrication and protection under normal operating conditions when the engine is warm.
On the other hand, 10W-30 oil has a slightly higher low-temperature viscosity compared to 5W-30 oil, as indicated by the first number (10). This means that it may flow slightly less easily in colder temperatures but is still suitable for most climates. The high-temperature viscosity is the same as 5W-30 oil, indicating that both oils provide similar protection when the engine is warm.
The choice between 5W-30 and 10W-30 depends on the manufacturer's recommendation for your specific vehicle. You can find this information in the owner's manual or by checking the oil cap or dipstick. Following the manufacturer's guidelines ensures that the oil used meets the necessary specifications and provides optimal lubrication and protection for your engine under varying temperatures.