* FTSEurofirst 300 index down 0.2 percent
* Tullow Oil, Antofagasta fall after results
* Natixis up after BPCE guarantees toxic assets
By Joanne Frearson
LONDON, Aug 26 (Reuters) - European equities dipped lower on Wednesday, snapping four straight sessions of rises as Ifo data from Germany failed to inspire investors, with commodity stocks the biggest losers.
By 0845 GMT, the pan-European FTSEurofirst 300 index of top shares was down 0.2 percent at 976.76 points after rising as high as 982.07 points earlier. The index, which plunged 45 percent in 2008, is up 17 percent this year having surged 51 percent from a record low in March.
"It looks like the market was preparing to sell off on those (Ifo) numbers," said an analyst, adding that the data probably came lower than the "whisper number" some traders were expecting.
The Munich-based think tank's business climate index, based on a monthly poll of some 7,000 firms, rose to 90.5 from an upwardly revised 87.4 in July.
"I am surprised that business expectations have once again improved so clearly," said Joerg Lueschow at WestLB.
"Nonetheless we remain somewhat sceptical as far as the medium-term outlook is concerned and still see considerable burdens for the German economy. It would not surprise us, if we see weaker Ifo data towards the end of the year."
Energy stocks were lower as crude steadied at around $72 a barrel after sliding 3 percent from its highest level since last October a day ago.
Tullow Oil lost 3.6 percent after it unveiled an 83 percent drop in profits on lower oil prices and production.
BG Group, BP, Royal Dutch Shell and Total were down 0.9 to 1.5 percent.
ANTOFAGASTA FALLS
Miners were lower, with Chilean copper miner Antofagasta down 2.3 percent after it posted lower-than-expected earnings per share in the first half and warned prices were likely to remain volatile in the second half.
BHP Billiton, Xstrata and Rio Tinto were down 0.4 to 1.5 percent.
Banks added the most points to the index. Natixis soared 33.4 percent after BPCE, formed from the merger this year of Caisse d'Epargne and Banque Populaire, said it will guarantee roughly 35 billion euros worth of toxic assets at the investment bank.
Royal Bank of Scotland, UniCredit and Lloyds Banking Group were up 1.7 to 5.2 percent.
The beverage sector was higher as Heineken gained 8.7 percent. The world's third-largest brewer reported a better-than-expected rise in first-half operating profit, driven by cost savings as volumes fell. Diageo, Carlsberg and SABMiller were up 0.7 to 2.7 percent.
Support services group Serco was 5.3 percent higher as first half profit came in ahead of forecasts and the company predicted cash-strapped governments will look to outsource business to preserve funds.
"The (Serco) shares trade on ... not much of a premium for a company with double-digit organic sales growth and rising margins. We think the story of public sector outsourcing is a good one," Cazenove analyst Robert Plant said in a note.
Across Europe, the FTSE 100 index was down 0.2 percent, Germany's DAX was 0.3 percent lower and France's CAC 40 was down 0.1 percent.
(Additional reporting Atul Prakash; editing by John Stonestreet)