High Quality Content by WIKIPEDIA articles! Crude oil benchmarks, also known as oil markers, were first introduced in the mid 1980s. There are three primary benchmarks, WTI, Brent Blend, and Dubai. Other well known blends include the Opec basket used by OPEC, Tapis Crude which is traded in Singapore, Bonny Light used in Nigeria and Mexico`s Isthmus. The Energy Intelligence Group has published a handbook which identifies 161 different blends in total.