A lot of people don't realize that Castrol is now owned by BP.
Castrol is famous for producing the first Group III hydrocracked mineral oil and to call it synthetic in their marketing (instead of using only Group IV PAO and Group V Esters). Now, most synthetics sold in the USA are Group III, although Mobil 1 has a blend of Groups III, IV, and V. Not sure about Castrol Edge with Titanium.
Pennzoil Platinum has a relatively new formulation that now comes in two different motor oils. Both are Group III made from natural gas using a process pioneered by Shell:
- Pennzoil Platinum with PurePlus Technology
- Pennzoil Ultra Platinum with PurePlus Technology