Confused about motor oil prices

[spinelll]

Please explain this equation to me:

• Crude oil price rises ($100+/barrel) = gasoline price rises ($4.00+/gal) = motor oil price rises ($4.24/qt). Understood.

• Crude oil price falls ($35/barrel) = gasoline price falls ($1.87/gal) = motor oil price remains the same ($4.24/qt). Not understood.

How is it that I’m paying $1.87 for a gallon of gas and $17.00 ($4.24/qt) for a gallon oil?