I see QS and Pennzoil similar to many auto manufacturers with their standard and premium offerings (i.e. Honda vs. Acura, Chevy vs. Buick, Nissan vs. Infiniti, etc.) The bones of the products are similar but with some unique features between the two with of course different marketing to target a different demographic. But dig deep, there's a lot of overlap/similarities between the two products. A top spec "standard" brand can out perform a base spec "premium" brand.
Look at Shell's product descriptions on their page. It's pretty clear on who they want to market their products to for the general public:
Quaker State:
Your vehicle works hard, your oil should too. Quaker State offers a complete line of motor oils, from full synthetic to high mileage to conventional, to protect passenger cars and light trucks and keep them running strong.
Pennzoil:
Pennzoil pushes the limits of technology. Breaking barriers, pioneering firsts, and defying convention is what we do best. As the number one name in motor oil, Pennzoil offers a range of innovative products to protect and optimize passenger vehicles and high-performance racing engines..
Certain QS products (QS Euro FS or UP FS) may have GTL but won't be advertised as such but Pennzoil not only has more GTL offerings (P Euro FS, UP FS, P FS) in more grades, but advertise as such because that's part of the tiered marketing strategy. Or do it a different way by changing the additive packaging to achieve the same goal of top licenses/approvals. But similar to auto manufacturers, there's some trickle down tech going on without the flashy marketing for the "lesser" brand. Unfortunately, we have less transparency with motor oils than auto manufacturer spec sheets and rely on word of mouth or VOA/UOA's to draw conclusions.
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