Oil shares accounted for just under half of the FTSE's closing gain, with BP up 2.5 percent and Shell up 1.6 percent as oil futures firmed, ending a five-day price slide.
The blue-chip index closed up 36.2 points at 4,490.1, its highest finish since June 29. That brought its gain on the week to just over 120 points, largely due to hopes of renewed economic growth after the sharp drop in crude oil prices over the week.
Graham Secker, UK equity strategist at investment bank Morgan Stanley, said recent gains felt reasonably solid and could make gains some months out.
"It's not overbought. Corporates are buying back stock; we've seen hefty buybacks in the last few weeks. There's good value here for people if they're willing to take a six-to-12-months view," said Secker.
"The main hurdle in the way of our call is if the oil price reverses its recent decline and starts nudging up to $50 (a barrel) again and people fret about the ability of the US economy to continue to recover next year," he said.
Britain's main gas and power utility, National Grid, closed 1.8 percent higher at 463-3/4 pence on hopes it would return cash to shareholders if it completes the sale of four of its UK gas networks - in the form of a special dividend or a share buyback.
The talk sharpened demand for other power stocks, with Scottish Power up 1.3 percent and Scottish & Southern Energy 1.7 percent higher.
Dealers also said Smith Barney, the research arm of US financial giant Citigroup, raised its target on NGT to 460p a share from 410p.
Drugs stocks helped the FTSE, with Europe's biggest drugmaker GlaxoSmithKline up 1 percent after it got off more lightly than expected in a US legal clash.
The company agreed to disclose information on all clinical studies of its drugs to settle the lawsuit. Investors had been braced for a lengthy and damaging court case.
Shares in mid-cap Dairy Crest tumbled 17.2 percent after Tesco, Britain's biggest supermarket, followed its rivals in streamlining its fresh milk suppliers.
Dairy Crest missed out as Tesco chose just two suppliers - Robert Wiseman, whose shares jumped 5.6 percent, and Arla, up 1.5 percent.