Petroleo Brasileiro PBR 0.16%, also known as Petrobras, was downgraded by Bank of America Merrill Lynch, Credit Suisse and Morgan Stanley Thursday after announcing that it will temporarily cut diesel prices in Brazil. Shares of the oil giant dropped 13.2 percent during pre-market trading to open at $13.11. The stock had previously been up 47 percent this year. SourceThere is still some downside potential due to stochastics.However, stochastics are getting closer to the oversold territory, so some upside can be expected sooner or later. $PBR, Petroleo Brasileiro S.A.- Petrobras / D