Mobil 1 0w-40 is the only Mobil 1 grade that doesn't have lower calcium and high magnesium. In fact it's very high on calcium, phos, zinc, etc...similar to Pennzoil/QS (no sodium or mg). So while Quaker State Ultimate Durability and Pennzoil Platinum would be the most similar in makeup, the Mobil 1 0w-40 might not be that far away. 3 Quaker State Ultimate Durability 5w30 and 1 Mobil 1 0w-40 will probably get you a PP-like additive package. I have no clue how effective it would be. I'd rather not mix but if you're mixing brands there are far worse choices.
The other Mobil 1 grades would fare better with Castrol with both of them being high mg / low calcium oils.