Deciding whether to switch to a different viscosity grade of engine oil, such as 5W-40 from 5W-30, typically depends on several factors, including the specific requirements of your vehicle and the prevailing climate conditions in your area. While I can provide some general guidance, it's important to consult your vehicle's owner's manual or speak with a qualified mechanic for advice tailored to your situation.
Both 5W-30 and 5W-40 are multi-viscosity oils that offer different characteristics. The numbers before the "W" indicate the oil's viscosity at low temperatures, while the numbers after the "W" represent the oil's viscosity at higher temperatures.
5W-30 oil is commonly recommended for most modern vehicles, as it provides good fuel efficiency and engine protection in a range of temperatures. It is suitable for many passenger cars and light trucks and is especially useful in colder climates where quick lubrication during cold starts is important.
5W-40 oil, on the other hand, has a slightly higher viscosity at high temperatures compared to 5W-30 oil. It may be recommended for vehicles that operate in hotter climates or endure heavy loads or towing. The higher viscosity can provide better protection under extreme conditions, but it may also lead to a slight decrease in fuel economy.
Switching to 5W-40 oil after hitting 120,000 miles may be a consideration if your vehicle's engine has experienced increased wear and tear over time, leading to slightly looser clearances between components. The higher viscosity of 5W-40 oil could provide improved lubrication and protection under these conditions. However, it's essential to review your vehicle's manual or consult a mechanic to ensure that a switch to 5W-40 oil is compatible with your engine.
Remember that using the manufacturer-recommended oil viscosity and following the recommended oil change intervals are vital for maintaining the performance and longevity of your engine.