What Is the Difference Between 5W30 & 20W50 Motor Oil?by Lexa W. Lee
The difference between 5W-30 and 20W-50 motor oil is in their viscosity rating at different temperatures.The first number is a temperature reading, the second is the viscosity rating. Viscosity refers to how easily an oil pours at a given temperature, according to "How To Pick The Right Motor Oil For Your Car" by Paul Weissler.
An oil rated 5W-30 is a multi-viscosity oil that can be used over a range of temperatures. The W stands for winter, and 5 is for 5 degrees Celsius, the lowest temperature at which the oil will pour. The number 30 means the oil will have a viscosity rating of 30 at 100 degrees Celsius.
A 20W-50 oil is a heavier multi-viscosity oil appropriate for higher temperatures and higher loads, which require a more viscous oil. The minimum temperature this oil will pour at is 20 degrees Celsius, and its viscosity rating at 100 degrees Celsius is 50.
Use in Cars
A 5W-30 oil is commonly used in passenger cars for normal use throughout the year. A 20W-50 oil will not protect a car as well in a cold winter and its greater viscosity will increase drag and friction in a passenger vehicle.
Lexa W. Lee is a New Orleans-based writer with more than 20 years of experience. She has contributed to "Central Nervous System News" and the "Journal of Naturopathic Medicine," as well as several online publications. Lee holds a Bachelor of Science in biology from Reed College, a naturopathic medical degree from the National College of Naturopathic Medicine and served as a postdoctoral researcher in immunology.