NEW YORK (MarketWatch) -- Crude-oil futures rose Monday for a sixth-straight session, climbing to their highest level in nearly seven months as China reported economic data showing expansion in manufacturing during May. That put the mainland's monthly string of manufacturing expansion at three, as two competing purchasing-manager indexes released Monday showed Chinese factory activity remained on an uptrend last month. The expansion in manufacturing indicated demand from the world's second-largest oil consumer may increase. Meanwhile, China also said it will increase gasoline and diesel prices. Crude for July delivery rose $1.64, or 2.5%, to $67.95 a barrel on the New York Mercantile Exchange. It surged as high as $68.29 earlier, the loftiest level for a front-month contract since early November. Natural gas for July delivery surged 25.5 cents, or 6.7%, to $4.09 per million British thermal units. Oil prices rallied 30% during May, the biggest monthly gain in a decade, on a weaker U.S. dollar and hopes for an economic recovery. Other commodities also made big gains. The Reuters/Jefferies CRB Index (CRB 398.28, +145.23, +57.39%) , which gauges the prices of 19 major commodities, surged 14% in May, the biggest monthly gain since 1974. Some analysts, however, were worried that oil's surge was overdone. "What all these surging markets have in common is that their advances are occurring in spite of uninspiring fundamentals," said Edward Meir, an analyst at MF Global, in a note. "It seems that for the moment participants are not interested in the bearish dynamics of the market, and instead are pushing values higher on solid technicals and bullish exogenous variables, such as the weaker dollar, firmer equity markets, and improving macro data," he added. The China Federation of Logistics & Purchasing's version of the PMI saw its benchmark reading fall to 53.1 in May from 53.5 in April, according to data released Monday. The reading marked the month in a row in which the gauge has held above 50, the level indicating expansion. See full story. China will increase gasoline and diesel prices by the equivalent of 19 cents a gallon, effective Monday, an official with a sales unit under PetroChina Co. in northern China said late Sunday. The move represents increases of about 6% to 7% over current average gasoline and diesel retail-ceiling benchmarks. See full story. Also on the data front, the U.S. personal-savings rate jumped to a 14-year high of 5.7% in April as after-tax incomes were boosted by provisions of the economic stimulus plan, the Commerce Department reported. See Economic Report. Meanwhile, U.S. manufacturers continued to cut back production in May, but not as rapidly as during the worst of the downturn, the Institute for Supply Management reported Monday. The ISM index rose to 42.8% in May from 40.1% in April. The rise was stronger than expected and the strongest since September. Also in Monday's trading, July reformulated gasoline gained 1.61 cents, or 0.9%, to $1.9114 a gallon and July heating oil futures rose 3.94 cents, or 2.4%, to $1.717 a gallon. In exchange-traded funds, the United States Oil Fund (USO 36.99, +0.59, +1.62%) , the biggest oil ETF, ended at $36.40 Friday.

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