The majority of motor oil freezes at approximately -90 degrees Fahrenheit. When oil has a higher number, it has a higher viscosity, meaning it is thicker, and its flow worsens as it gets colder.
The "W" present on motor oil labels indicates that the oil is able to tolerate both severely cold and severely hot temperatures. It means that there are special plastics in the oil that scientists add to it in a laboratory. During extreme conditions, this plastic helps to stabilize the oil and make it less vulnerable to extreme shifts by offering a degree of stability to it.