Should the Encore use 5W30 or 5W40 engine oil?

[VonColin]

The Encore uses 5W-30 full synthetic engine oil. Below are specific introductions to engine oil types: 1. Mineral oil: Derived from crude oil refining. Typically low-cost, but mineral oil base oxidizes easily. All mineral oils contain various imported additives with a service life of approximately six months. 2. Semi-synthetic oil: Higher refining cost but offers excellent oxidation resistance, making it a high-quality long-duration oil with a service life of about twelve months. Considering the balance between price and quality, semi-synthetic oil has the widest application range. 3. Full synthetic oil: Chemically synthesized oil that maintains lubrication even when base oils fail.

[LaAlessandra]

I've been driving the Encore for three years and have always used 5W30 oil. The GM official manual clearly recommends this viscosity, especially for the 1.3T engine model. The 30-grade oil flows faster during cold starts, providing instant lubrication to critical engine components when starting a cold engine. Moreover, during city traffic jams, the fuel consumption is about 0.5L lower compared to 40-grade oil. Last time during maintenance, the mechanic mentioned that older cars with significant engine wear might consider using 40-grade oil, but my car has only run 60,000 kilometers, so it's completely unnecessary. While 40-grade oil offers slightly better high-temperature protection during long summer trips, the difference is minimal for daily driving, and the factory-certified 5W30 full synthetic oil is more than sufficient.

[JohnDella]

Last week, I changed the engine oil for my 2014 Buick Encore. The 4S dealership insisted on using 5W30, claiming it suits both turbocharged and naturally aspirated models of this car. Compared to 40 viscosity oil, 30 has less pumping resistance during cold starts, making winter ignition smoother in northern regions. The mechanic said unless there's significant engine wear (like in vehicles over ten years old), 40 viscosity isn't necessary, as thicker oil films can increase fuel consumption. I'm currently using SN-grade full synthetic 5W30, and the oil temperature remains stable even when cruising at 120 km/h on the highway, so there's no need to change viscosity just for peace of mind.

[Elena]

Before changing the engine oil, I did a lot of research. The L3G engine of the Encore was originally designed to match with 5W30. The high-temperature viscosity HTHS value of 30 is around 3.5, which just meets the requirements of turbocharged engines, while the 40 viscosity exceeds 4.0, which is excessive. A neighbor who is a car mechanic said that in high-temperature areas of the south, 40 could be considered, but actual tests in Guangzhou summers showed that 30 is completely sufficient. The Mobil ESP 5W30 with General Motors dexos1 certification has strong shear resistance and is much more reliable than no-name 40 oils.

[DelColeman]

I specifically asked the mechanic about the principle during maintenance: The '5' before the W represents -30°C fluidity, with no difference between the two. However, 30 has lower high-temperature viscosity than 40. The new Enclave engine has high precision, and using 40 increases crankshaft operating resistance, with actual tests showing an additional 0.4 liters of fuel consumption per 100 kilometers. Last time, I switched to 5W40 for three months and felt the acceleration became sluggish. After switching back to 30, it immediately felt more responsive. The manual specifies 5W30, and using 40 might affect the warranty, so it's better to be cautious.