NEW YORK ( TheStreet) -TheStreet Ratings' stock model upgraded Exxon Mobil ( XOM) to 'Buy' from 'Hold'. Net income at this $315 billion market cap, oil & natural gas giant nearly doubled by rising 97.3% to $7.6 billion in second quarter over the prior second quarter. TheStreet Ratings released rating changes on nine additional U.S. common stocks for September 28, 2010. In total, two three stocks were downgraded and eight stocks have been upgraded by our stock model. Second quarter revenue at Exxon Mobil grew by 25.5% to $82.7 billion over the same quarter last year. Learn more about Exxon Mobil: Company Profile, Income Statement, Balance Sheet, Stock Ratios, Analyst Ratings. In another upgrade, shares of L.B. Foster Company ( FSTR) have moved to 'Buy' from 'Hold'. Second quarter net income jumped by 126% to a profit of $6 million compared to the year ago quarter. Over the same period, revenue rose by 20.3% to $120 million. Learn more about L.B. Foster Company: Company Profile, Income Statement, Balance Sheet, Stock Ratios, Analyst Ratings. -- Reported by Kevin Baker in Jupiter, Fla. For additional Investment Research check out our Ratings Research Center.