Petrofac, Tullow Oil, BP, Shell and a host of stocks exposed to the oil price were suffering heavy losses on Friday.Oil and gas engineer Weir, however, was bouncing back after recent declines following an upgrade by Canaccord Genuity from 'hold' to 'buy'. The broker said the stock's valuation now looks "compelling" after having fallen by over a third over the past three months alone.Utility stocks were mixed with United Utilities and Severn Trent gaining despite Ofwat's announcement that average water bills will drop by 5% by 2019-2020.However, SSE was lower after it was named as one of the three energy providers being fined a combined £4.6m by Ofgem for failing to meet environmental targets.FTSE 100 - RisersUnited Utilities Group (UU.) 905.50p +3.84%Severn Trent (SVT) 1,954.00p +2.04%Weir Group (WEIR) 1,708.00p +0.77%Sainsbury (J) (SBRY) 228.00p +0.75%Tullow Oil (TLW) 373.80p +0.27%FTSE 100 - FallersPetrofac Ltd. (PFC) 687.00p -5.11%Coca-Cola HBC AG (CDI) (CCH) 1,273.00p -4.14%St James's Place (STJ) 781.50p -2.98%Anglo American (AAL) 1,140.50p -2.77%Aviva (AV.) 473.70p -2.75%Randgold Resources Ltd. (RRS) 4,145.00p -2.72%Smiths Group (SMIN) 1,031.00p -2.55%Schroders (SDR) 2,579.00p -2.42%Intertek Group (ITRK) 2,167.00p -2.39%Whitbread (WTB) 4,496.00p -2.37%