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

Alliance Holdings‘s (NASDAQ:AHGP) grade is moving up to a B (“buy”) this week from last week’s C (“hold”). Alliance Holdings produces and markets coal to utilities and industrial users in the United States. In Portfolio Grader’s specific subcategories of Earnings Revisions and Equity, AHGP also gets A’s. The stock’s dividend yield is 2.8%. For more information, get Portfolio Grader’s complete analysis of AHGP stock.

Tesoro (NYSE:TSO) is progressing from last week’s rating of B (“buy”) as the company improves to an A (“strong buy”) this week. Tesoro is an independent company that refines crude oil, sells refined products in bulk and sells motor fuels on the retail market. The stock has a trailing PE Ratio of 8.7. For more information, get Portfolio Grader’s complete analysis of TSO stock.

The rating of Global Partners (NYSE:GLP) moves up this week, rising from a B to an A. Global Partners owns, controls or has access to a terminal network of refined petroleum products in New England, located in the United States. The current dividend yield is 2.1%. For more information, get Portfolio Grader’s complete analysis of GLP stock.

Chesapeake Midstream Partners (NYSE:CHKM) boosts its rating from a C to a B 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.

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.