A study by Ricardo for the Renewable Fuels Association (RFA) concludes that the adoption of E15 as the blend limit for standard US pump grades of gasoline rather than the current E10 should not adversely affect vehicles manufactured between 1994 and 2000 in terms of their performance and durability based on normal specifications and usage profile.
Given that result, Ricardo said, it can reasonably be concluded that these vehicles do not represent an obstacle to raising the blend limit to E15 from the E10 that currently forms the basis of much of the commercially available US gasoline motor fuel.
The US EPA is currently reviewing a waiver for E15 use in light duty motor vehicles; the agency has stated that an approval of E15 may be limited to 2001 or 2007 model year (MY) and newer vehicles. However, the RFA contends that limiting the use of E15 to certain model year vehicles may prevent widespread availability and implementation.
While significant research efforts have been made to date in studies sponsored by the US Department of Energy and other government and industry bodies evaluating the potential impact of E15 on 2001 model year and newer vehicles, minimal engineering analysis has previously been focused on earlier model year vehicles.
However, the model years 1994 to 2000 inclusive represent a total of 62.8 million vehicles or approximately 25% of the current overall US light duty vehicle fleet.
Ricardo’s approach in the study was to:
- Identify and review fuel system hardware changes occurring in 1994 – 2000 MY
- Review EPA emission and diagnostic regulation adoption and implementation
- Interrogate EPA emissions certification data to evaluate tailpipe emissions effects
- Study after treatment systems and vehicle calibration data from 1994 – 2000 MY
- Identify characteristics of E15 fuel blends that affect hardware durability
- Identify degradation mechanisms of fuel systems and evaluate E15 effect
- Procure and evaluate physical fuel system parts from focus model years
In keeping with the spirit of Environmental Protection Agency’s longstanding policy, Ricardo used a “reliable statistical sampling” approach to the analysis of the national fleet was used. Sales trends by both calendar year and model year were studied to identify the highest volume sales of the automotive manufacturers between 1994 and 2000. Six automotive manufacturers (General Motors, Ford, Chrysler, Toyota, Honda, Nissan) were identified as representing the overwhelming majority of vehicles sales for the study period (87.5%), and the top selling platforms of these manufacturers thus became the focus of the Ricardo study.
This approach enabled Ricardo to carry its engineering analysis without individually inspecting or testing each of this very large number of vehicles.
Among the conclusions of the report were:
Fuel systems in the 1994 to 2000 MY timeframe changed dramatically due to the onset of enhanced evaporative emissions and on-board refueling vapor recovery ORVR regulations, Ricardo noted. In general these changes increased the tolerance of fuel and vapor handling systems to ethanol blended fuels. Ricardo said that its review of actual vehicle hardware, from vehicles manufactured prior to the onset of these regulations, indicated that pre-enhanced evaporative emission systems were able to handle the current E10 fuel formulation and would not be expected to have further detrimental effects from the introduction of E15.
Vehicles from the study period were emissions-certified with relatively large compliance margins. As mileage and time have accumulated, the emissions reduction potential of the aftertreatment systems has degraded, but not to the point where the majority of the vehicles are out of compliance. In order to trigger a MIL (Malfunction Indicator Lamp), in general, a copious increase in any particular emissions species caused by a move from E10 to E15 would be required. This makes illumination of the MIL due to emissions non-compliance highly unlikely.
A review of vehicle calibrations from the 1994 to 2000 MY timeframe found that implementation of E15 into the light duty vehicle fleet will not have a significant effect on aftertreatment and calibration variables compared to E10.
A comparison of the properties of gasoline blends, E0, E10, and E15, was completed. It was found that E15 has a lower heating value (LHV) than E10 by ~1.9%. Therefore, the implementation of E15 in the passenger car fleet will cause a reduction in vehicle mileage (miles / gallon) by the same percentage.
Physical test results generally concluded that the materials in use in fuel systems components during this time period would not undergo significant changes when exposed to E15 compared to when they are exposed to E10.
An inspection of some physical fuel system hardware from vehicles represented by the top 25 vehicle platforms from the 1994 to 2000 MY found that none of the physical hardware in the fuel systems was fully compliant with enhanced evaporative emissions legislation, evidenced by the absence of engineered quick connects on many of the connections around the fuel tank and vapor lines. Therefore, this sample of vehicle hardware represents the vehicles that are less likely to be tolerant to ethanol blends. However, these potentially less robust systems show no ill effects from exposure to E10. It is not expected that further degradation will be experienced when these systems are exposed to E15, Ricardo said.
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Older vehicles represent a significant yet previously comparatively under-researched element of the US national vehicle fleet. In considering the potential risks and benefits of increasing the current ethanol blend ceiling in regular gasoline from 10 to 15 percent it is crucial that the interests of the potentially very large stakeholder group represented by the owners of these vehicles are investigated. While many previous studies by Ricardo and others have evaluated the impact of higher ethanol blends on newer vehicles, this study demonstrates for the first time that raising the blend ceiling to E15 is likely to have a negligible impact on vehicles manufactured between 1994 and 2000.—Ricardo, Inc. President Kent Niederhofer