High-quality: WTI Is taken into account a "light-weight sweet" crude oil, and that is much easier to refine, though Brent is a mixture of crude oils, together with both of those "gentle sweet" and "significant sour" grades. Screening is by references that POs talk to each other for, not by https://maps.app.goo.gl/VhAGTRCDGTuVhHJa8