What is SL5W-40 engine oil?
2 Answers
S stands for gasoline engine oil, L represents the quality level, 5W indicates low-temperature resistance down to -30 degrees Celsius (calculated as 5-35=-30; for example, 0W40 would be 0-35=-35 degrees Celsius). The "W" denotes Winter, and 40 represents the high-temperature viscosity, which determines the oil film strength and the thickness of the lubricating oil. SL5W-40 is a standard set by the American Petroleum Institute (API) + SAE, and this oil is commonly referred to as all-season engine oil. Below are the functions of engine oil: 1. Friction reduction: A sufficiently thick oil film separates the surfaces of relatively sliding parts, thereby reducing wear. 2. Sealing: Engine oil can form a seal between the piston rings and pistons, reducing gas leakage and preventing external contaminants from entering. 3. Rust prevention: Lubricating oil adheres to part surfaces, preventing contact with water, air, acidic substances, and harmful gases. 4. Cushioning: When the pressure in the engine cylinder rises sharply, suddenly increasing the load on the pistons, piston rings, connecting rods, and crankshaft bearings, this load is transmitted through bearing lubrication, cushioning the impact load. 5. Cleaning: High-quality engine oil can carry carbon deposits, sludge, and worn metal particles from engine parts back to the oil tank through circulation, and the flow of the lubricating oil washes away dirt generated on the working surfaces of the parts.
SL5W-40 is a common type of engine oil that I've been using in my car for over a decade. It performs particularly well in cold winter conditions. The 'SL' refers to the API (American Petroleum Institute) standard, suitable for regular gasoline engines, representing an older but reliable grade that protects engine components against corrosion and wear. The '5W-40' denotes the viscosity grade: the '5W' indicates excellent low-temperature fluidity, ensuring quick lubrication during cold winter starts to minimize engine wear; the '40' represents high-temperature viscosity, maintaining stable engine protection without thinning out in summer heat. This oil suits most common household vehicles—I've used it in my previous Toyotas and Hondas—with typical oil change intervals between 5,000 to 8,000 kilometers. However, for older vehicles or high-mileage usage, always consult your owner's manual for manufacturer recommendations rather than making arbitrary changes. Using the correct oil can extend engine life and save fuel costs.
