This week, the overall grades of 15 oil and gas stocks are lower, according to the Portfolio Grader database. Each of these rates a “D” (“sell”) or “F” overall (“strong sell”).

Crescent Point Energy Corp.’s (CPG) rating falls this week to an F (“strong sell”), down from last week’s D (“sell”). In Portfolio Grader’s specific subcategories of Earnings Revisions, Earnings Surprise, Cash Flow and Margin Growth, CPG also gets F’s. The stock’s trailing PE Ratio is 110.80. For more information, get Portfolio Grader’s complete analysis of CPG stock.

Golar LNG Partners (GMLP) is on the decline this week, earning a D (“sell”) after receiving a C (“hold”) last week. Golar LNG Partners owns floating storage and regasification units and liquefied natural gas carriers. To get an in-depth look at GMLP, get Portfolio Grader’s complete analysis of GMLP stock.

The rating of Cosan Limited Class A (CZZ) slips from a D to an F. Cosan is a fully integrated company in the renewable energy and infrastructure segments in Brazil. The stock gets F’s in Cash Flow and Margin Growth. The trailing PE Ratio for the stock is 39.80. For more information, get Portfolio Grader’s complete analysis of CZZ stock.

Goodrich Petroleum Corporation (GDP) earns a D this week, moving down from last week’s grade of C. Goodrich Petroleum explores, develops, produces and acquires oil and natural gas properties. The stock gets F’s in Earnings Growth, Earnings Revisions, Equity and Cash Flow. As of July 18, 2014, 25.2% of outstanding Goodrich Petroleum Corporation shares were held short. Shares of the stock are changing hands at twice the rate they were a week ago. To get an in-depth look at GDP, get Portfolio Grader’s complete analysis of GDP stock.

This week, EXCO Resources, Inc. (XCO) drops from a D to an F rating. EXCO Resources is an oil and natural gas company involved in the exploration, exploitation, development and production of onshore North American oil and natural gas properties. The stock gets F’s in Earnings Surprise, Equity and Cash Flow. As of July 18, 2014, 10.8% of outstanding EXCO Resources, Inc. shares were held short. Shares of the stock have been changing hands at an unusually rapid pace, twice the rate of the week prior. For more information, get Portfolio Grader’s complete analysis of XCO stock.

Calumet Specialty Products Partners, L.P. (CLMT) gets weaker ratings this week as last week’s D drops to an F. Calumet Specialty Products produces hydrocarbon products in North America. The stock gets F’s in Earnings Growth, Earnings Momentum and Earnings Revisions. Cash Flow and Margin Growth also get F’s. To get an in-depth look at CLMT, get Portfolio Grader’s complete analysis of CLMT stock.

The rating of Plains All American Pipeline, L.P. (PAA) declines this week from a C to a D. Plains All American Pipeline is involved in interstate and intrastate crude oil pipeline transportation and crude oil terminalling storage activities. The stock currently has a trailing PE Ratio of 26.00. For more information, get Portfolio Grader’s complete analysis of PAA stock.

TransCanada Corporation’s (TRP) rating weakens this week, dropping to an F versus last week’s D. TransCanada develops and operates energy infrastructures, including natural gas pipelines. To get an in-depth look at TRP, get Portfolio Grader’s complete analysis of TRP stock.

Enbridge (ENB) experiences a ratings drop this week, going from last week’s D to an F. Enbridge is in the business of transportation and distribution of crude oil and natural gas primarily in Canada and the United States. The stock gets F’s in Earnings Growth, Earnings Momentum and Cash Flow. Shares of the stock have been trading at an exceptionally rapid pace, up twofold from the week prior. The stock’s trailing PE Ratio is 71.00. For more information, get Portfolio Grader’s complete analysis of ENB stock.

This week, StealthGas’ (GASS) rating worsens to a D from the company’s C rating a week ago. StealthGas offers marine transport services for liquefied petroleum gas producers and users. In Earnings Growth, Earnings Revisions, Earnings Surprise and Cash Flow the stock gets F’s. To get an in-depth look at GASS, get Portfolio Grader’s complete analysis of GASS stock.

Slipping from a D to an F rating, Ultrapar Participacoes S.A. Sponsored ADR (UGP) takes a hit this week. Ultrapar Participacoes is engaged in the fuel distribution and chemical businesses in Brazil. For more information, get Portfolio Grader’s complete analysis of UGP stock.

Gevo (GEVO) is having a tough week. The company’s rating falls from a D to an F. Gevo operates as a technology development company for biobutanol. The stock gets F’s in Equity, Cash Flow and Sales Growth. As of July 18, 2014, 10.5% of outstanding Gevo shares were held short. To get an in-depth look at GEVO, get Portfolio Grader’s complete analysis of GEVO stock.

PDC Energy (PETD) earns a D this week, falling from last week’s grade of C. PDC Energy is an oil and gas company with drilling and production operations in the Rocky Mountains, the Appalachian Basin and Michigan. The stock gets F’s in Earnings Revisions and Cash Flow. As of July 18, 2014, 11% of outstanding PDC Energy shares were held short. For more information, get Portfolio Grader’s complete analysis of PETD stock.

Chevron Corporation’s (CVX) rating weakens this week, dropping to an F versus last week’s D. Chevron is an integrated energy company with operations in countries located around the world. To get an in-depth look at CVX, get Portfolio Grader’s complete analysis of CVX stock.

The rating of Kinder Morgan, Inc. Class P (KMI) slips from a D to an F. Kinder Morgan is a pipeline transportation and energy storage company. Shares of the stock have been trading at an exceptionally rapid pace, up threefold from the week prior. The stock has a trailing PE Ratio of 32.10. For more information, get Portfolio Grader’s complete analysis of KMI 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.