Leading shares are holding on to early gains helped by a rally in the price of crude oil, which has buoyed the prices of majors BP and BG as well as a host of second-liners.News coming out of the G20 summit in Pittsburgh is making the headlines with consensus already reached on boosting the influence of emerging countries by making the G20 rather than G7 or G8 the key forum for big global discussions.Away from Pittsburgh, oil groups are going well despite the steady decline in the price of crude over the past few days. It dropped below $66 per barrel last night but has recovered a tad this morning. Tullow Oil and Cairn Energy are the best performers in the sector, though the big guns BP and BG are also firmer. Tullow gets a lift from Goldman Sachs raising its target price to 1396p from 1160p.Oilfield support services group Petrofac is given the cold shoulder, however, after Goldman Sachs downgraded the stock to 'neutral' following the share's recent good run. Merrill Lynch has gone further still and has cut its rating for Petrofac to 'underperform'.Elsewhere in the oil sector Dana Petroleum is lower after drilling of a wildcat well in Norway drew a blank. Tate & Lyle expects operating profit for the half year to be broadly in line with last year, but the sugar and sweeteners group cautioned that a number of its markets remain challenging.There's a 'significant risk' that nightclub operator Luminar will miss full year expectations after a grim few months at the end of the first half sent like for like sales down 5.9% in the 26 weeks to 27 August. They fell 4.5% when adjusted for the late August bank holiday. September has been even worse, especially weekend admissions. Avalon, a company owned by Permira Advisers, has reached an agreement to buy Just Retirement for about £229.6m. Avalon will pay 76p for each share in Just Retirement, which today posted a full-year loss of £3m.Sales remain under pressure at plumbing supplies distributor BSS with the group still predicting little pick-up before the end of the year. Total revenue for the 25-week period ended 19 September was £608.7m, 3.9% down on last year on an equivalent trading day basis, with a like-for-like decrease of 6.9%, BSS said. Plumbers merchant Wolseley falls in sympathy.Business publisher Euromoney is the best performer today after it forecast pre-tax profits in the year ended 30 September would beat expectations.