* The "W" stands for Winter: The number before the "W" indicates the oil's viscosity at low temperatures. Both 10W-30 and 10W-40 have the same low-temperature viscosity rating of 10. This means they flow readily when the engine is cold, providing quicker lubrication and easier starting in cold weather.
* The second number (30 and 40) indicates the oil's viscosity at high temperatures: This is the more significant difference. A 40-weight oil is thicker at high operating temperatures than a 30-weight oil.
Here's a summary of the key differences:
* High-Temperature Viscosity: 10W-40 is thicker at high temperatures than 10W-30. This means 10W-40 provides a stronger oil film to protect engine parts at high operating temperatures and under heavy loads.
* Engine Protection: The thicker 10W-40 offers potentially better protection against wear in high-stress situations, such as towing or driving in hot climates.
* Fuel Economy: The thinner 10W-30 might offer slightly better fuel economy because it requires less energy to pump through the engine.
* Application: 10W-30 is generally suitable for most vehicles, especially those driven in moderate climates and under normal conditions. 10W-40 is often recommended for vehicles that experience higher operating temperatures, high mileage, or heavy-duty use. Always check your owner's manual for the specific viscosity grade recommended for your vehicle.
In short: Choose 10W-40 for potentially better high-temperature protection, and 10W-30 for potentially better fuel economy (though the difference is often minimal). The best choice depends on your vehicle, its usage, and your climate. Always consult your owner's manual.
