Engineering giant GKN was leading the risers after Credit Suisse upgraded the stock from neutral to outperform, saying the the company is in 'pole position' to acquire Volvo Aero Engines. Temporary power and temperature control solutions group Aggreko was also rising, following reports of a "very strong" first quarter, with both International Power Projects and the Local business growing underlying revenues by over a fifth. Meanwhile, Anglo-Dutch integrated oil company Royal Dutch Shell has deployed a vessel to investigate an oil sheen in the Gulf of Mexico close to two of its oil platforms.Shell said there is no evidence that the sheen, which covers an area about one-mile-by-ten, emanated from any of its platforms. "The source and type of sheen is currently unknown," said Kelly op de Weegh, a spokeswoman for Shell. FTSE 100 - RisersGKN (GKN) 199.90p +4.39%ITV (ITV) 85.65p +3.07%Rio Tinto (RIO) 3,427.00p +2.71%Aggreko (AGK) 2,216.00p +2.64%Johnson Matthey (JMAT) 2,322.00p +2.38%Croda International (CRDA) 2,118.00p +2.37%Wolseley (WOS) 2,345.00p +2.22%Meggitt (MGGT) 403.40p +2.18%Petrofac Ltd. (PFC) 1,711.00p +2.15%BT Group (BT.A) 217.70p +2.11%FTSE 100 - FallersMan Group (EMG) 112.00p -3.20%Royal Dutch Shell 'A' (RDSA) 2,092.00p -2.29%Royal Dutch Shell 'B' (RDSB) 2,137.00p -2.20%Resolution Ltd. (RSL) 246.30p -1.72%Aviva (AV.) 308.20p -1.41%BP (BP.) 438.35p -1.33%Legal & General Group (LGEN) 123.20p -0.96%British Land Co (BLND) 471.00p -0.82%Centrica (CNA) 314.30p -0.79%Evraz (EVR) 350.50p -0.76%NR