Oil capped its steepest weekly loss since March as the International Energy Agency forecast prices will need to fall further to curb excess supplies. The world remains “massively oversupplied” before markets tighten in 2016 when output growth outside OPEC grinds to a halt, the IEA said in a monthly report Friday. Crude has given up this year’s gains following China’s equities rout and the turmoil in Greece.