* Oil prices dive to lowest in more than 5 weeks
* U.S. gasoline stocks build shocks during driving season
* Charts show Brent, U.S. crude in oversold territory (New throughout, updates prices and market activity)
By Scott DiSavino
NEW YORK, June 14 (Reuters) - Oil prices sank more than 3 percent to their lowest in more than five weeks on Wednesday following U.S. data showing an unexpectedly large weekly build in U.S. gasoline inventories and International Energy Agency (IEA)data projecting a big increase in non-OPEC output in 2018.
The increase in U.S. gasoline inventories drove down RBOB futures by more than 4 percent, tugging Brent and U.S. crude futures lower with them, analysts said.
"The industry continues to turn a crude oil surplus into a gasoline and distillate product surplus," Andrew Lipow, president of Lipow Oil Associates in Houston said.
After rising for three consecutive days, Brent futures were down $1.81, or 3.7 percent, at $46.91 by 12:44 p.m. EDT (1644 GMT). U.S. West Texas Intermediate crude was down $1.75, or 3.8 percent, at $44.71 per barrel.
Both contracts hit their lowest since May 5, driving them into technically oversold territory.
The U.S. Energy Information Administration (EIA) said gasoline inventories increased by 2.1 million barrels during the week ended June 9, while crude inventories decreased by 1.7 million barrels.
That compares with analysts estimates in a Reuters poll for a 0.5 million barrel draw in gasoline stocks and a 2.7 million barrel draw in crude inventories.
OPEC and other exporters such as Russia have agreed to keep production almost 1.8 million barrels per day (bpd) below the levels pumped at the end of last year and not to increase output until the end of the first quarter of 2018.
But adherence to the cuts is under scrutiny and the producer group said this week its output rose by 336,000 bpd in May to 32.14 million bpd.
Oil inventories are near record highs in some parts of the world, and producers outside the OPEC deal are increasing output.
The IEA said in a separate report earlier Wednesday it expected growth in non-OPEC supply to outpace demand growth next year.
"Our first outlook for 2018 makes sobering reading for those producers looking to restrain supply," the IEA said in its monthly oil market report.
A rapid rise in U.S. shale oil output will contribute to the increase in non-OPEC supply next year, the IEA said.
"The outlook for oil hinges on the effectiveness of the OPEC cuts relative to the supply increases from U.S. shale," said William O'Loughlin, analyst at Australia's Rivkin Securities.
Global demand continues to grow, but not by enough to get rid of the glut.
Demand grew 1 percent in 2016, roughly in line with the previous two years, but well below the 10-year average of 1.8 percent, BP said in its benchmark Statistical Review of World Energy on Tuesday.
Additional reporting by Amanda Cooper and Christopher Johnson in London and Henning Gloystein in Singapore; Editing by Dale Hudson, David Clarke and David Gregorio