The world's two largest oil markets are Brent traded at the London IPE and West Texas Intermediate (WTI) traded at the New York NYMEX. The spread can heavily influence the underlying contracts.
The spread between the two has been Brent over WTI for the majority of the past 7 years. In late 2015 we saw the spread flip. With the US gasoline contract based on the NY Harbor landing the Brent relationship has a large linkage to that contract also.