I painted my brothers s-10 long box with 2 qt.
of PPG base(1:1.5) and 3qt. of DuPont 7600 clear(4:1).
It was everything but the inside of the box and roof.
I also painted my old van (GMC Safari) with PPG DCC and it also took 2 qt.(4:1:2).
That's my exp. but ezrider is right, it's not always cut and dry.