What does the 'W' in motor oil stand for?

[GabrielleDella]

In motor oil, 'W' stands for Winter. The functions of motor oil are: 1. Lubrication and friction reduction; 2. Assisting in cooling and temperature reduction; 3. Sealing and leak prevention; 4. Rust and corrosion protection; 5. Shock absorption and cushioning. Classification of motor oil: 1. Conventional mineral oil; 2. Semi-synthetic oil; 3. Full synthetic oil. The method for changing motor oil is: 1. Lift the vehicle, remove the undercarriage shield, and place a container of about 10 liters under the oil drain plug; 2. Unscrew the oil drain plug, use an air gun to blow into the oil filler opening for two minutes, then tighten the oil drain plug after draining and wipe it with a tissue to check for leaks; 3. Reinstall the undercarriage shield and lower the vehicle, then use a funnel to add oil through the filler opening.

[JuniperLee]

The 'W' in motor oil actually stands for Winter, indicating how well the oil performs in cold weather. Last winter when I drove my old car up north, I noticed it had trouble starting. It wasn't until I asked the mechanic during an oil change that I understood: The lower the number before the W (like 0W or 5W), the better the oil flows at low temperatures, making engine starts smoother. Higher numbers like 10W or even 15W mean poorer cold-weather flow, making them unsuitable for frigid regions. This directly impacts engine protection by preventing cold-start wear. The numbers after (like 30, 40) represent high-temperature viscosity, controlling oil film thickness to prevent overheating damage. Choosing oil depends on local climate - 0W-30 works great in the north, while 5W-40 suffices in the south. I also recommend regular oil level checks: Pull the dipstick after parking for 30 minutes to ensure mid-range levels. Timely oil changes prevent degradation and extend engine life.

[DelLevi]

As someone who frequently works on cars, let me explain the meaning of W: It stands for Winter. In oil grades like 5W-30, the W indicates low-temperature fluidity. A lower number means easier cold starts, which is especially important for older cars in extremely cold regions. The combination of numbers before and after the W represents the oil's viscosity range, ensuring engine protection in both cold and hot conditions. A common misconception is focusing only on the high-temperature number while ignoring the W. In reality, a higher W like 10W means the oil is too thick during cold starts, potentially damaging the engine. Always follow the vehicle owner's manual for oil selection and avoid mixing different types. Regular maintenance is crucial—change the oil every 5,000 km or six months, and check the filter. In rainy areas, be mindful of oil contamination and clean the engine compartment promptly.

[StBrooklyn]

Having used family cars for over a decade, my experience tells me that the 'W' in oil grades indicates winter performance. For example, my car's 5W-20 means quick starts in winter with non-sticky oil to prevent engine freezing. I worry about wrong oil choices causing wear, so I check local minimum temperatures before selecting oil – in cold regions, lower 'W' like 0W-40 is safer. The 'W' part relates to viscosity index; lower numbers mean better flow, aiding fuel efficiency and emission reduction. The number after 'W' controls high-temperature protection – avoid exceeding RPMs during daily drives. I've developed a habit of checking the dipstick quarterly; sufficient level means normal. Change oil more frequently than six months to reduce engine aging. Note: substandard oil harms the environment, so choose branded products.