Phillips 66 shares dipped briefly in light volume after an analyst at Barclays downgraded the stock earlier in the day.
"Although we think the stock will continue to trade at a premium to the group and that its well-diversified business is capable of weathering cyclical volatility better than other pure play refiners, we see limited upside," Paul Cheng wrote in a Wednesday research note.
Phillips 66 also announced a 63 cent per share quarterly dividend, payable Sept. 1. The energy manufacturing company's shares are down over the past year, as oil has struggled to recover from historic lows.
Agricultural company Monsanto's stock edged higher in light trading volume after unconfirmed reports that it would revive talks with BASF over a Bayer alternative. Bloomberg reported the news, building on prior reports this spring that Bayer and BASF wanted to buy Monsanto. Bayer declined to comment on the report, citing a policy against commenting on market rumors.
CNBC has reached out to Monsanto and BASF for comment.
Meanwhile, Congress is considering a national labeling standard for food containing genetically-modified organisms, which could affect the food industry.
CSX's shares pared some gains after hours, ticking slightly lower after its earnings were released unexpectedly before the closing bell. The railroad and transportation company's stock rose 4.4 percent in the regular trading session after the company posted its earnings earlier than expected.
CSX reported earnings of 47 cents per share, compared to Wall Street expectations of 44 cents, according to a Thomson Reuters consensus estimate. CSX posted revenue of $2.7 billion for the quarter, slightly above expectations for $2.69 billion.