like 0W-20 and 5W-30, we'd have to use different weight oils for various climates. If you lived in the middle of the United States, you would often use a different weight engine oil in the summer ...

However, if your car normally requires the use of 5W-20, it's dangerously low on ... temperature swings you could use the same weight, or viscosity, oil all year. In the Midwest United States ...