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SAE High Octane Fuels Symposium: Is a new high-octane fuel a pragmatic pathway for higher engine efficiency in the US? (part 2)

As highlighted at the 2013 SAE International High Octane Fuels Symposium (HOF) last week, high octane fuels—combined with optimized engines—are viable enablers to higher efficiency operation. When ethanol is used as the octane enhancer, there is an added benefit due to the latent heat of vaporization of that fuel. (Earlier post.)

As articulated by Dr. Jim Szybist from Oak Ridge National Laboratory (ORNL), one vision of a high-octane ethanol fuel infrastructure and distribution system could include a standardized high ethanol/high octane fuel with ethanol content probably in the E20-E50 range. Refiners would continue to produce two high volume products in the gasoline boiling range: the Exx BOB (Blendstock for Oxygenate Blending) would have a low octane requirement (e.g., RON ~85), and be inexpensive for refiners to produce. Gasoline or E10 BOB would be premium-grade fuel for total coverage of legacy fleet.

(BOB is unfinished gasoline which will later be blended with an oxygenate such as ethanol.)

Such a scenario would cause minimal disruption to the ~150,000 US fueling stations and overall distribution system, Szybist suggested, as the majority of fueling stations in the US have 2 underground storage tanks (regular and premium) and the two tanks would be converted to a low-ethanol fuel for the legacy fleet and a high octane fuel for newer vehicles.

Among the benefits of such an approach (which was echoed by William Woebkenberg from Mercedes-Benz Research & Development North America), would be enabling OEMs to design higher efficiency engines and vehicle systems necessary to meet upcoming CAFE targets. The transition, Szybist noted, would have to occur rapidly, and potentially include all OEMs, perhaps through the designation of the high-octane blend as the LEV III fuel.

However, presenters from the automotive, refining, and convenience store (the convenience store industry sells more than 80% of the fuel in the US) industries raised several challenges and issues to the practical implementation of such an approach.

Dr. Coleman Jones, GM North America’s Biofuel Implementation Manager, began by outlining the thicket of emissions testing requirements and Federal and California certification fuels. On the Federal Tier 2 side, these include E0: 93 RON min, 9 psi RVP; Cold CO Premium: 92 AKI, 11.5 psi RVP; Cold CO Regular: 88 AKI, 11.5 psi RVP; E85: 7 psi RVP, 85% EtOH; and E10: 10 psi RVP (used for E85 evaporative emissions).

California certification fuels incude: Phase 2: 7 psi RVP, 11% MTBE; 91 AKI, min; Phase 3 Regular: 7 psi RVP, 10% EtOH, 88 AKI; Phase 3 Premium: 7 psi RVP, 10% EtOH, 91 AKI; and E85: 8.25 psi RVP, 82% EtOH.

The market is changing, Jones noted. Recent increases in ethanol usage have made E0 and MTBE rare in the US. California has moved to require E10 as its new certification fuel, and EPA is considering moving its certification E0 gasoline to E15 and its certification E85 to E83. The California ARB has introduced regular and premium certification fuel, and EPA has indicated that it is planning to do the same. This, Jones noted, will more clearly separate premium and regular fuel vehicles.

A new certification fuel reflecting a new high octane market fuel might have several advantages, Jones suggested. First, a certification fuel might focus the market on a certain composition. Second, certifying a vehicle to new, more stringent emissions standards may be easier with the new fuel than with E85.

However, he asked, would this mean that the industry would then have three certification fuels: E85, Gasoline, and the new fuel? Other questions he raised were:

  • Would OEMs be able to pick any one, two or three for certification?

  • Would all tests be required on all fuels?

  • What benefit would there be for certifying a new fuel?

  • Would there be compensation for the lower energy content of the new fuel in fuel economy calculations?

  • How would there be “harmonization” with CARB and LEVIII?

  • What would be the regulatory effects of mis-fueling?

In a move to such a third fuel, a clear implementation plan and policy framework would need to be defined and agreed upon by all key stakeholders, he suggested. Very critically, there must be a benefit to customer for a dedicated future fuel vehicle—i.e., lower cost to operate and/or improved performance.

If a clear plan and policy framework cannot be created and achieved then Flexfuel vehicles that are engineered to run on a wide variety of fuels will remain the only viable option...There are many uncertainties regarding how it would be implemented in the certification process and in the field. We are all going to need to work together to develop a clear executable implementation plan. And I didn’t even cover how we are going to do this at retail.

—Coleman Jones

James Uihlein, Fuels Technology Advisor, Chevron Corporation, noted that the new Federal CAFE rulemaking did not identify any new fuel requirements. Further, although a Federal Tier 3 rulemaking has not yet been released, CARB has approved its LEV III regulations, and expressed the belief that LEV III will be at least as stringent as Tier 3. However, the current LEV III regulations do not include any new fuel requirements, either. Certification fuels are being updated to represent current in-use gasoline—i.e., with ethanol content.

Setting aside the issue of ethanol as an octane-enhancing blendstock, Uihlein observed that delivering a higher octane fuel out of the refinery increases the greenhouse gas footprint of the fuel, as more octane requires more processing.

This was reinforced by Jeffrey Farenback-Brateman, Gasoline Team Lead form ExonMobil Research and Engineering Company, who cited work done by the Japan Clean Air Program (JCAP) showing that an increase in RON from 90 to 95 resulted in a well-to-wheels net increase in GHG of around 1.5%.

Both Uihlein and Farenback-Brateman suggested that vehicle technologies to meet CAFE and Tier 3/LEV III will not require new fuels. A future fuel would require the evaluation of benefits beyond current CAFE and Tier 3/LEV III, Uihlein suggested, including the cost effectiveness of those benefits compared to other options.

John Eichenberger, VP of Government Relations for the National Association of Convenience Stores (NACS) began by observing that the convenience store industry in the US sells more than 80% of the fuel in the US annually. (Integrated oil companies own & operate 0.4% of retail fuel outlets.) Of the 149,220 convenience stores, 123,289 sell fuel. Of those, 58.6% are 1-store operations. Fuel sales generate 71% of their sales, but only 38% of profit.

Eichenberger suggested that the big issues for the retailers in moving to such as new fuel would be infrastructure cost (equipment must be UL-listed for the fuels they handle), liability for misfueling, and, of course, customer demand.

We need to figure out a way to allow those dispensers and tanks out there that are compatible to be legally recognized as compatible so that we can bring these products into our stores without having to replace perfectly good equipment. And we can be assured that we are not going to be nailed because we did so. We need to make sure that if we do everything we possibly can to prevent misfueling, and somebody ignores or deliberately, we need to be protected as well.

—John Eichenberger



Would improved fuels burn 'cleaner' and pollute less?

Roger Pham

The answer is no.
The most fuel-efficient engine, the Atkinson-cycle engine in the Prius with CR of 10 and ER of 13 prefers 87-octane fuel. With 90 octane, efficiency is dropped by 10% and 93 octane drops efficiency further. Future direct-injection engine with CR of 12 and ER of 15 will increase efficiency further without requiring higher octane fuels than 87. Of course,higher octane fuel will allow even higher CR and ER, perhaps to CR of 14 and ER of 18, or even CR of 15 and ER of 20, but then, you will run the risk of exhaust too cool for the Catalytic converter.

Furthermore, higher ethanol content is a no no, given the tight food supply situation and future risk of droughts.


Roger, what would it take, in your estimation, to make the Volkswagen 1.4L TSI (turbo) engine, as found in the 2013 Jetta Hybrid, to run on 87 octane instead of the required 91 octane?

Roger Pham

Water and alcohol injection at higher loads, in proper proportion.


Roger, sounds reasonable. The Jetta Hybrid already gets 44-48 mpg (actually more when I drove it, more like 50+ mpg), but the requirement for premium (91 octane) gasoline is a drawback.

Henry Gibson

The future of automotive fuels should be jet fuel or its close relative Diesel. Zero octane! They can be produced most cheaply. Both Capstone turbines and Bladon Jets have demonstrated hybrid turbine automobiles. Capstone has many turbines in hybrid buses all with very low emissions. Innas NOAX demonstrated its diesel free-piston hydraulic pump that can be combined with Artemis hydraulic motors and pumps for double efficiency and a very simple engine with low emissions and few parts with very low brake wear and low cost high performance hydraulic systems. Perhaps someone will make an efficient turbine powered hydraulic pump. Bladon engineers can do it the quickest. ..HG..

Roger Pham

Depending on the type of crude oil, there will need be some lighter-molecular-weight hydrocarbon like gasoline after hydrocracking and fractional distillation, as well heavier chains like diesel and kerosene. There is nothing wrong with gasoline as a fuel. Gasoline is cheaper than diesel on per-gallon basis, and gasoline engines cost a lot less than diesel engines. Advanced turbo-charged and downsized automotive gasoline engines are almost as efficient as turbo-diesel engines, or are already there, if one consider the higher energy content per gallon of diesel fuel. For non-turbocharged engines, Atkinson-cycle gasoline engine can match the efficiency of non-turbocharged diesel engine.

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