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’s trailing PE Ratio is 87.10. To get an in-depth look at CPG, 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. For more information, get Portfolio Grader’s complete analysis of GMLP stock.

This week, Cosan Limited Class A (CZZ) drops from a D to an F rating. 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. To get an in-depth look at CZZ, get Portfolio Grader’s complete analysis of CZZ stock.

Goodrich Petroleum Corporation (GDP) earns a D this week, falling from last week’s grade of C. Goodrich Petroleum explores, develops, produces and acquires oil and natural gas properties. In Earnings Growth, Earnings Revisions, Equity and Cash Flow the stock gets F’s. As of Sept. 26, 2014, 32.5% of outstanding Goodrich Petroleum Corporation shares were held short. For more information, get Portfolio Grader’s complete analysis of GDP stock.

EXCO Resources, Inc.’s (XCO) rating weakens this week, dropping to an F versus last week’s D. 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 Sept. 26, 2014, 13.3% of outstanding EXCO Resources, Inc. shares were held short. To get an in-depth look at XCO, get Portfolio Grader’s complete analysis of XCO stock.

Calumet Specialty Products Partners, L.P. (CLMT) earns an F this week, moving down from last week’s grade of D. 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. For more information, get Portfolio Grader’s complete analysis of CLMT stock.

This is a rough week for Plains All American Pipeline, L.P. (PAA). The company’s rating falls to D from the previous week’s C. Plains All American Pipeline is involved in interstate and intrastate crude oil pipeline transportation and crude oil terminalling storage activities. The trailing PE Ratio for the stock is 26.90. To get an in-depth look at PAA, get Portfolio Grader’s complete analysis of PAA stock.

Slipping from a D to an F rating, TransCanada Corporation (TRP) takes a hit this week. TransCanada develops and operates energy infrastructures, including natural gas pipelines. For more information, get Portfolio Grader’s complete analysis of TRP stock.

The rating of Enbridge (ENB) slips from a 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. The stock currently has a trailing PE Ratio of 32.90. To get an in-depth look at ENB, get Portfolio Grader’s complete analysis of ENB stock.

StealthGas (GASS) gets weaker ratings this week as last week’s C drops to a D. StealthGas offers marine transport services for liquefied petroleum gas producers and users. The stock receives F’s in Earnings Growth, Earnings Revisions, Earnings Surprise and Cash Flow. For more information, get Portfolio Grader’s complete analysis of GASS stock.

The rating of Ultrapar Participacoes S.A. Sponsored ADR (UGP) declines this week from a D to an F. Ultrapar Participacoes is engaged in the fuel distribution and chemical businesses in Brazil. To get an in-depth look at UGP, 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. For more information, get Portfolio Grader’s complete analysis of GEVO stock.

PDC Energy (PETD) earns a D this week, moving down 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. To get an in-depth look at PETD, get Portfolio Grader’s complete analysis of PETD stock.

The rating of Chevron Corporation (CVX) slips from a D to an F. Chevron is an integrated energy company with operations in countries located around the world. For more information, get Portfolio Grader’s complete analysis of CVX stock.

This is a rough week for Kinder Morgan, Inc. Class P (KMI). The company’s rating falls to F from the previous week’s D. Kinder Morgan is a pipeline transportation and energy storage company. The stock’s trailing PE Ratio is 33.60. To get an in-depth look at KMI, 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.