This week, four Oil and Gas stocks are improving their overall ratings on Portfolio Grader. Each of these stocks is rated an “A” (“strong buy”) or “B” overall (“buy”).

Chesapeake Midstream Partners (NYSE:CHKM) is making progress this week as its rating of C (“hold”) from last week increases to a B (“buy”) rating this week. Chesapeake Midstream Partners owns, operates, develops, and acquires natural gas, natural gas liquids, and oil gathering systems, as well as other midstream energy assets in the United States. For more information, get Portfolio Grader’s complete analysis of CHKM stock.

This week, Oiltanking Partners LP (NYSE:OILT) is showing good progress as the company’s rating jumps from a B (“buy”) last week to an A (“strong buy”). Oiltanking Partners engages in the terminaling, storage and transportation of crude oil, refined petroleum products and liquefied petroleum gas. For more information, get Portfolio Grader’s complete analysis of OILT stock.

Cabot Oil & Gas (NYSE:COG) improves from a B to an A rating this week. Cabot Oil & Gas is an independent company that develops, explores, produces and markets natural gas, and transports, stores, and gathers it for resale. For more information, get Portfolio Grader’s complete analysis of COG stock.

This week, L&L Energy’s (NASDAQ:LLEN) ratings are up from a B last week to an A. L&L Energy acquires, invests in and operates growing energy entities and coal mines in the People’s Republic of China. For more information, get Portfolio Grader’s complete analysis of LLEN stock.

Louis Navellier’s proprietary Portfolio Grader stock ranking system assesses roughly 5,000 companies every week based on a number of fundamental and quantitative measures. Stocks are given a letter grade based on their results — with A being “strong buy,” and F being “strong sell.” Explore the tool here.