Oil Refining Margins - Regional. $US per barrel. The refining margins presented are benchmark margins for three major global refining centres; US Gulf Coast (USGC), North West Europe (NWE - Rotterdam) and Singapore. In each case they are based on a single crude oil appropriate for that region and have optimized product yields based on a generic refinery configuration (cracking, hydrocracking or coking), again appropriate for that region. The margins are on a semi-variable basis, ie the margin after all variable costs and fixed energy costs.