UPDATE 1-Big CFTC data revision raises oil traders' eyebrows

(Adds comment by CFTC commissioner, additional information from spokeswoman)

By Robert Campbell

NEW YORK, Aug 5 (Reuters) - A quiet data revision that has boosted by nearly 25 percent the number of oil futures contracts U.S. regulators think are held by speculators is raising eyebrows in the energy trading community.

The revision means that speculators controlled 48 percent of the open interest in NYMEX crude oil futures and options as of July 15, compared with just over 38 percent under the previous classification.

"That's huge when you look at the numbers," said Phil Flynn of Alaron Trading in Chicago.

"It changes the whole way you look at the recent moves in this market."

The U.S. Commodities Futures Trading Commission announced on July 18 that it was reclassifying some trading positions that it had reported as commercial hedging positions as noncommercial speculative positions.

The data revision converted approximately 327,000 long and 330,000 short NYMEX crude oil futures and options positions into mostly spreading positions held by speculators.

The big shift is all the more surprising, oil traders and analysts said, since the CFTC apparently reclassified only one unidentified oil trader at the same time as the data revision.