What type of oil does a 2007 Audi A4 take?

"5W30- Use Castrol GTX"

Not entirely true.

5w40 is the viscosity necessary for the 2007 a4. Castrol GTX synthetic "The black bottle" is what the stores call them.

5w30 is a substitute if you cant find the right viscosity to top off with, however, if you are doing a full oil change and expect the car to work the same way, plus maintain the warranty, because they can test for this, use the correct oil.