WASHINGTON — After carefully reviewing 43 studies on the effects of E15 on engine durability, emissions, and other factors, the National Renewable Energy Laboratory (NREL) issued a report finding that the available literature “…did not show meaningful differences between E15 and E10 in any performance category.” With respect to the Coordinating Research Council’s (CRC) controversial engine durability study, NREL found “…the conclusion that engines will experience mechanical engine failure when operating on E15 is not supported by the data.”

The objective of the NREL review was to assess the research conducted to date applicable to the effects of E15 use in model year 2001 and newer vehicles, including the aspects that were not a part of EPA’s considerations when approving E15. Specifically, NREL reviewed 33 unique research studies, as well as 10 related reviews, studies of methodology, or duplicate presentations of the same research data. Further underscoring EPA approval of the safety and efficacy of E15, NREL experts found that 2001 and newer vehicles are well equipped to adapt to the ethanol content in both E10 and E15. The engine performance and durability expectations from the materials compatibility and emissions test results (for E15) are confirmed by studies of fuel system, engine and whole vehicle durability. The fact that there are 33 unique studies focused on materials compatibility, engine and fuel system durability, exhaust emissions, catalyst durability, effects on on-board diagnostics and evaporative emissions seems lost on the emphasis placed on one refuted study.

According to Bob Dinneen, President and CEO of the Renewable Fuels Association, “The disputed CRC engine durability study has been at the center of Big Oil’s political crusade against E15, and policymakers have been given the false impression that the CRC project is the one and only study that has been conducted on E15. Nothing could be further from the truth. The NREL report reflects a substantial review of literature on E15 research showing no meaningful concern with using the fuel and exposes the many methodological shortcomings of studies API is citing on engine durability.”

Dinneen continued, “It’s time for Big Oil to stop using actors to scare people about E15. It’s time they start paying attention to the overwhelming data and real world experience demonstrating the efficacy of E15.” The NREL report identified numerous flaws and gaps in several of the studies reviewed.  For the CRC engine durability study these include:

  • Faulty leakdown failure criteria. Most of the “failures” on E15 and E20 were related to engines that did not pass an arbitrary cylinder “leakdown” test. While other tests in the CRC study used established standards from OEMs and EPA, the leakdown test utilized arbitrary criteria with no scientific basis. According to NREL, “CRC selected a 10% leakdown failure limit, more restrictive (50% below) than that of the lowest value specified by OEMs for engines in the study.”
  • Failure to use E10 as a control fuel. Engines that “failed” on E20 or E15 were subsequently tested on E0, but not on E10 (despite the fact that E10 is the predominant in-use fuel today). This approach presumes that failures were related to ethanol content, rather than any number of other factors that could have caused the failure.
  • Inappropriate statistical analysis. The CRC study used assumed values (i.e., “dummy data”) for vehicles that were not actually tested. These dummy values demonstrated consistent bias in relation to the question that the analysis was intended to determine.

“By critically examining the universe of studies on mid-level ethanol blends, the NREL report brings important context and scientific credibility back to the debate over E15,” Dinneen said. “In addition to providing an appreciation for the entire body of scientific work on E15, the report will undoubtedly assist policymakers and the public in recognizing the substantial body of research that has been conducted on E15 showing no evidence of deterioration in engine durability or maintenance issues.”

The NREL study was sponsored by the Renewable Fuels Association. View the study and its appendix.