This week, seven oil and gas stocks are improving their overall rating on Portfolio Grader. Each of these rates an “A” (“strong buy”) or “B” overall (“buy”).

This week, Chesapeake Midstream Partners (CHKM) is showing significant improvement as the company’s rating hops from a C (“hold”) to a B (“buy”). 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, PVR Partners, L.P. (PVR) pushes up from a C to a B rating. PVR Partners owns and operates a network of natural gas pipelines and processing plants that provide gathering, transportation, compression, processing, dehydration and related services to natural gas producers. At present, the stock has a dividend yield of 2.2%. For more information, get Portfolio Grader’s complete analysis of PVR stock.

The rating of PBF Energy, Inc. Class A (PBF) moves up this week, rising from a C to a B. PBF Energy operates as an independent petroleum refiner and supplier of unbranded transportation fuels, heating oil, petrochemical feedstocks, lubricants and other petroleum products in the United States. For more information, get Portfolio Grader’s complete analysis of PBF stock.

This week, Vertex Energy, Inc.’s (VTNR) ratings are up from a C last week to a B. Vertex Energy is a middle market consolidator, refiner and re-refiner of distressed petroleum streams, such as used oil, transmix, fuel oils and off-specification commercial chemical products. For more information, get Portfolio Grader’s complete analysis of VTNR stock.

Rose Rock Midstream, L.P. (RRMS) boosts its rating from a C to a B this week. Rose Rock Midstream engages in the gathering, transportation, storage, distribution, and marketing of crude oil in Colorado, Kansas, Minnesota, Montana, North Dakota, Oklahoma, and Texas. The current dividend yield is 2.5%. For more information, get Portfolio Grader’s complete analysis of RRMS stock.

Alliance Resource Partners, L.P. (ARLP) earns a B this week, jumping up from last week’s grade of C. Alliance Resource Partners produces and markets coal, primarily to major United States utilities and industrial users. The stock’s dividend yield is 2.6%. For more information, get Portfolio Grader’s complete analysis of ARLP stock.

This is a strong week for U.S. Energy Corp. (USEG). The company’s rating climbs to B from the previous week’s C. U. S. Energy explores for oil and natural gas. For more information, get Portfolio Grader’s complete analysis of USEG 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.