Made by does not mean same as.
Yes, Car Quest Oil (and NAPA oil, as well as a few others) are made by Ashland, who also is the maker of Valvoline. It does not automatically mean it is Valvoline.
As stated above, Ashland themselves say it is not the same, PDS shows some differences, and VOA have shown some differences between Valvoline and NAPA (not sure about Car Quest). NAPA is a close cousin to Valvoline, it is a high sodium oil just like Valvoline. Car Quest is probably the same as NAPA. It is a good lube and I would have no problem using it if it was cheap enough.