Unless you are living in the North Pole, a zero weight oil isn't really necessary, but........yes, a lot of people use it.
It's very thin at startup, so in cold weather it makes it easier for the engine to turn over. The weight of the oil has
nothing to do with the oil change interval. Apples and oranges. By and large, dealerships are the most expensive way
to go for most things. Some people like them. Some don't.