What does 5W mean in motor oil?

[VincentAnn]

The meaning of 5W in motor oil is that 5W is just a temperature grade, representing the minimum applicable temperature of the oil. Below this temperature, the oil becomes very viscous and loses its normal flow capability. The number 5 indicates that the minimum applicable temperature of the oil is -30 degrees Celsius. For example, in the winter outdoors in northern China, if the temperature drops below -30 degrees Celsius, using 5W oil after the vehicle has been parked for a long time can be very troublesome. Oil viscosity specifications: In fact, there are many types of viscosity specifications. Different types of oil have their own characteristics. Taking 5W30 oil as a reference, the letter "W" stands for Winter, while the "5" represents the cold-start performance of the oil. The smaller the number, the stronger the oil's cold resistance, allowing the engine to start easily even at very low temperatures. The last number "30" represents the kinematic viscosity standard at 100 degrees Celsius (between 9.3mm2/s and 12.5mm2/s). Oil classification: High-temperature types for summer use include 20, 30, 40, and 50. The larger the number, the higher the viscosity and the maximum applicable temperature. Low-temperature types for winter use include 0W, 5W, 10W, 15W, 20W, and 25W. The symbol "W" stands for Winter, and the smaller the number before "W," the lower the low-temperature viscosity and the better the low-temperature flow performance, meaning it can be used at lower minimum temperatures. All-season types suitable for both winter and summer include 5W-20, 5W-30, 5W-40, 5W-50, 10W-20, 10W-30, 10W-40, and 10W-50, among others. The smaller the number before "W," the lower the minimum applicable temperature of the oil, and the larger the number after the hyphen, the higher the maximum applicable temperature.

[GarrettLee]

I've been driving for over a decade and often change my own oil. The 5W rating actually indicates the oil's low-temperature fluidity. The 'W' stands for winter, and the lower the number in front, the better it performs in cold weather. 5W oil won't solidify at -30°C and can quickly lubricate the engine during cold starts. Here in the north where winter temperatures drop below -20°C, 5W oil protects the engine instantly at startup, preventing dry friction. If you switch to 10W oil, it might struggle at -25°C. When choosing oil, don't just focus on this number—there's also the high-temperature viscosity rating like 30 or 40, which should match the manufacturer's recommendation. Older cars benefit from thicker oil for better protection, while newer cars run more efficiently with thinner oil for better fuel economy. Even when driving on highways in summer temperatures above 35°C, there's no need to worry about the oil being too thin—just pay attention to the certification standards.

[LeAbigail]

Recently, while researching motor oil in the garage, I discovered that the '5' in 5w represents low-temperature performance. It ensures smooth flow to every corner of the engine during cold starts, preventing dry friction damage to parts. I compared data between 0w and 10w: 0w is the most cold-resistant, down to -35°C, but significantly more expensive, while 10w is cheaper but struggles to start below -20°C. For most regions, 5w strikes a good balance between price and performance. However, it's important to pay attention to the full viscosity grade, such as 5w-30, where the high-temperature viscosity has a kinematic viscosity of 9.3 to 12.5 centistokes at 100°C. Changing the oil without replacing the filter reduces effectiveness—if the filter is clogged, even the best oil won't help. The viscosity specified in the manual is the most accurate; don't arbitrarily upgrade the grade.

[Maya]

Last time during maintenance, the mechanic taught me that the '5W' in '5W-30' on the oil bottle refers to its low-temperature performance. The few seconds when starting the car on winter mornings are the most critical. 5W can instantly pump and lubricate at temperatures as low as -30°C, reducing wear. In the south, 10W might be acceptable, but in the north, 5W is a must. My old car has been running on 5W-30 for eight years, starting up immediately in winter with no issues, which is very reassuring. However, some newer car models now require 0W-20 for better fuel efficiency. As for oil change intervals, it depends on the oil quality—full synthetic oils can go up to 10,000 kilometers without a problem.

[DelAvery]

I like to think of engine oil as honey. 5W is like thin honey that doesn't solidify in winter. The number 5 represents fluidity, making it easier to protect the engine on cold mornings compared to 10W. When choosing oil, you need to look at two numbers - for example, the 30 in 5W-30 represents high-temperature viscosity. Last time I mistakenly used 5W-40, and fuel consumption noticeably increased. New car manuals always recommend specific viscosities - modern engines have high precision, and using oil that's too thick can actually damage them. Also, certification marks are more important than brands - look for standards like API SP or SN.

[Dias]

Driving in Northeast China gives me a deep understanding. 5W oil can still flow normally at -25°C. One year, I mistakenly used 10W oil and couldn't start the car at -30°C. Later, I learned that the W in 5W stands for winter. For every decrease of 5 in the number, the cold resistance improves by about 5 degrees. However, just changing the oil without maintenance is useless. I always replace the filter every 8,000 kilometers. Nowadays, fully synthetic 5W-30 oil is suitable for all seasons, unlike in the past when we had to switch between different oils for winter and summer. Older cars with larger piston gaps can use 40 viscosity, while newer cars with 20 viscosity are more fuel-efficient. Friends in the north should opt for 0W for better safety.