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

Crescent Point Energy Corp. (CPG) earns an F (“strong sell”) this week, moving down from last week’s grade of 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 currently has a trailing PE Ratio of 108.50. To get an in-depth look at CPG, get Portfolio Grader’s complete analysis of CPG stock.

This week, Golar LNG Partners (GMLP) falls to a D (“sell”), worse than last week’s grade of C (“hold”). Golar LNG Partners owns floating storage and regasification units and liquefied natural gas carriers. For more information, get Portfolio Grader’s complete analysis of GMLP stock.

Kinder Morgan, Inc. Class P (KMI) earns an F this week, falling from last week’s grade of D. Kinder Morgan is a pipeline transportation and energy storage company. The stock’s trailing PE Ratio is 29.30. For a full analysis of KMI stock, visit Portfolio Grader.

Slipping from a D to an F rating, Cosan Limited Class A (CZZ) takes a hit this week. 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 stock has a trailing PE Ratio of 39.50. For more information, get Portfolio Grader’s complete analysis of CZZ stock.

Goodrich Petroleum Corporation’s (GDP) rating weakens this week, dropping to a D versus last week’s C. Goodrich Petroleum explores, develops, produces and acquires oil and natural gas properties. The stock receives F’s in Earnings Growth, Earnings Revisions, Equity and Cash Flow. As of April 25, 2014, 35.6% of outstanding Goodrich Petroleum Corporation shares were held short. To get an in-depth look at GDP, get Portfolio Grader’s complete analysis of GDP stock.

The rating of EXCO Resources, Inc. (XCO) slips from a D to an F. 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 April 25, 2014, 15.5% of outstanding EXCO Resources, Inc. shares were held short. The trailing PE Ratio for the stock is 54.20. For a full analysis of XCO stock, visit Portfolio Grader.

Calumet Specialty Products Partners, L.P. (CLMT) experiences a ratings drop this week, going from last week’s D 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 Chevron Corporation (CVX) declines this week from a D to an F. Chevron is an integrated energy company with operations in countries located around the world. For a full analysis of CVX stock, visit Portfolio Grader.

Plains All American Pipeline, L.P. (PAA) gets weaker ratings this week as last week’s C drops to a D. Plains All American Pipeline is involved in interstate and intrastate crude oil pipeline transportation and crude oil terminalling storage activities. For more information, get Portfolio Grader’s complete analysis of PAA stock.

This week, TransCanada Corporation’s (TRP) rating worsens to an F from the company’s D rating a week ago. TransCanada develops and operates energy infrastructures, including natural gas pipelines. The stock’s trailing PE Ratio is 27.10. For a full analysis of TRP stock, visit Portfolio Grader.

This week, Enbridge (ENB) drops from a D to an F rating. 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. The stock currently has a trailing PE Ratio of 84.30. For more information, get Portfolio Grader’s complete analysis of ENB stock.

This is a rough week for StealthGas (GASS). The company’s rating falls to D from the previous week’s C. 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. Shares of the stock have been trading at an exceptionally rapid pace, up twofold from the week prior. To get an in-depth look at GASS, get Portfolio Grader’s complete analysis of GASS stock.

Ultrapar Participacoes S.A. Sponsored ADR (UGP) is having a tough week. The company’s rating falls from a D to an F. Ultrapar Participacoes is engaged in the fuel distribution and chemical businesses in Brazil. For a full analysis of UGP stock, visit Portfolio Grader.

Gevo (GEVO) earns an F this week, falling from last week’s grade of D. Gevo operates as a technology development company for biobutanol. The stock gets F’s in Equity, Cash Flow and Sales Growth. As of April 25, 2014, 10.4% of outstanding Gevo shares were held short. To get an in-depth look at GEVO, get Portfolio Grader’s complete analysis of GEVO stock.

This is a rough week for PDC Energy (PETD). The company’s rating falls to D from the previous week’s 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 April 25, 2014, 11.1% of outstanding PDC Energy shares were held short. For more information, get Portfolio Grader’s complete analysis of PETD 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.