Muffins:Coffee :: Cars:?

Muffins and coffee are often enjoyed together, making them complementary goods. When the demand for coffee increases, people are likely to buy more muffins to go with it. Similarly, cars and gasoline are complementary goods because when more people buy cars, the demand for gasoline usually goes up as well. For example, if a new car model becomes very popular, more people will need gas to drive those cars. So, just like muffins and coffee, cars and gasoline are connected in how their demand affects each other.