NEW YORK ( TheStreet) -- Crude oil prices slumped to $84 a barrel Monday as a stronger greenback made dollar-priced commodities less attractive to foreign buyers. Although the June delivery contract for crude traded as high as $85.63 on Monday, it finished only a little higher than its lowest point of the session: $84.06. The contract lost 92 cents, or 1.1%, to settle at $84.20 a barrel -- a disappointing turn after its performance on Friday, when it added $1.42 to settle at $85.12 a barrel on surging new-home sales and strong durable goods orders. A strong U.S. dollar, which was trading 0.3% higher against a basket of foreign currencies for most of the session, was putting some downward pressure on crude. The dollar index was last up by 0.1%. The dollar was picking up against the euro, in particular, as concerns arose about how and when a financial rescue package to aid Greece will become ratified. Stocks failed to establish a clear direction Monday. The Dow spent the session in positive territory, supported by strong earnings results from Caterpillar ( CAT) while other major U.S. indices were pressured by concerns about tightened financial regulations. Oil-related stocks were moving both above and below the flat line, with the NYSE Arca Oil index losing 0.5% and the Philadelphia Oil Service Sector index dropping 0.4%. Exxon Mobil ( XOM) and ConocoPhillips ( COP) were the only oil majors to close slightly ahead Monday. This week is a big one for major oil firms, which are set to report earnings news. National Oilwell Varco ( NOV) and Valero ( VLO) will report before Tuesday's opening bell. On Wednesday, Hess ( HES) will offer its first-quarter assessment in the morning. Integrated majors ConocoPhillips and Exxon Mobil will be joined by Apache ( APA), Smith International ( SII) and BJ Services ( BJS) in reporting Thursday morning. By the late afternoon, the market will hear from refiners Sunoco ( SUN) and Tesoro ( TSO), which are each expected to report losses. Dow component Chevron will cap the week's oil-related releases by reporting Friday. Shares of Schlumberger ( SLB), which received a price target and earnings estimate lift at Citi , added a penny, or 0.01%, at $72.69. Elsewhere, workers were attempting to contain an oil leak off the Gulf of Mexico, according to multiple reports, that is unleashing some 1,000 barrels of oil a day into the water. The spill began after an oil rig controlled by Transocean ( RIG), which was then leased out to BP ( BP), experienced an explosion and sunk late last week. The Associated Press reported the leak could take months to completely fix. Shares of natural gas alternative fuel provider Clean Energy Fuels ( CLNE) lost 9% as the climate bill stalled in Washington. Elsewhere, the natural gas contract for May delivery gained nearly a penny, or 0.1%, to settle at $4.26 per million British thermal units. The June heating oil contract shed a penny, or 0.6%, to settle at $2.24 a gallon, while June gasoline also lost a penny, or 0.6%, to settle at $2.35 a gallon. --Written by Sung Moss and Melinda Peer in New York.