The problem isn’t ethanol, it’s BOB

The GAfuels Blog is written by two private pilots concerned about the future availability of fuels for piston-engine aircraft: Dean Billing, Sisters, Ore., an expert on autogas and ethanol, and Kent Misegades, Cary, N.C., an aerospace engineer and aviation journalist.

The aviation alphabets and pilots need to understand something about ethanol-blended gasoline and blending laws:  Although ethanol will be blended into every drop of gasoline by the end of 2011 or early 2012, that’s not the problem! That is the unintended consequence of a deeply flawed federal Renewable Fuel Standard mandated deep inside a huge act called EISA 2007.  There is a table in the RFS section that is driving the ethanol blending madness and it is cast in stone.

What is ironic is that renewable fuel is defined in the act as E85. E10 is never mentioned and EISA 2007 is not a mandatory E10 law.  There is no federal mandatory E10 law.  There are only seven state mandatory E10 laws and, of those, only four are currently active: Minnesota, Hawaii, Missouri and Oregon. Washington has a wimpy mandatory volumetric ethanol law of 2%, which they have tried to repeal because it means nothing now in light of the run-amok federal RFS act.  The fifth mandatory E10 law will be in Florida and it will become effective on the last day of this year. Congratulations to my friends in Florida: You get a useless law. Montana and Pennsylvania have untriggered mandatory E10 laws and Louisiana has an untriggered volumetric ethanol law. These laws will probably never trigger.

Most everyone knows that gasoline refineries do not make E10. The only products that refineries make are gasoline or Blendstock for Oxygenated Blending (BOB).  That’s it!  They have nothing to do with ethanol. No gasoline refinery makes ethanol and they don’t allow ethanol-blended gasoline to be shipped through their pipelines, for a number of reasons, the primary one being corrosion.

Ethanol is made by bio-fuel producers, some of which are now owned by oil companies as separate subsidiaries because the handwriting is on the wall: All gasoline will have to be E10 within the next two years. Ethanol is trucked, barged or moved by rail to terminals where gasoline or BOB from the refinery is blended with the ethanol and then distributed to service stations as E10, or maybe a tiny amount of E85. All E10 is made at the terminal, not the refinery. Ethanol can be combined with gasoline to make E10 by a process called “splash blending”, but that is inefficient, more expensive and it is harder to meet air quality requirements and other ASTM standards for finished gasoline, so E10 is usually made by combining ethanol with BOB, which is designed for ethanol blending, resulting in finished legal E10 gasoline. Splash blending is declining, while blending ethanol with BOB is spreading.

Here is the problem with BOB:

First, BOB always has a lower “octane.” Ethanol has very high octane and adding 10% by volume to gasoline raises the Anti Knock Index (AKI) about 3 points, so the BOB used to make regular grade gasoline is generally 84 AKI, and the BOB used to make premium gasoline is never higher that 90 AKI.

Second, this is what the Director of the Division of Air Resources, New York State Department of Environmental Conservation, stated in his E15 waiver comments:

“E10 is not simply ethanol added to finished gasoline. Since most gasoline at retail contains ethanol, the industry factors the addition of ethanol into the formulation of the petroleum-based portion of the final blend. The chemical properties of ethanol and its dilution impact allow refiners to produce a petroleum-based blendstock which when combined with a specified amount of ethanol (or other oxygenate) results in a final blend with the desired legal and market properties. The petroleum-based blendstock, in most cases, would not qualify as gasoline or be legal to sell as gasoline. For RFG this blendstock is RBOB. For conventional gasoline it is CBOB,  and for California RFG it is CaRBOB.”

So this is the future for sport aviation, as all of the gasoline becomes E10 because of the unintended consequences of a federal act that was supposed to spur the production, distribution and use of E85 and flex-fuel vehicles: The refineries will no longer produce any 91+ AKI premium unleaded gasoline. There will be no need too, because there are no federal or state statutes that require them to provide it.  BOB is cheaper to make, E10 is more profitable to sell. Consequently, kiss your STC goodbye and your LSA will have to limp along on 100LL with an octane it doesn’t need and an additive that will increase your maintenance significantly and pollute the environment with lead that the EPA is trying to stop.

If you are in an aviation alphabet, the FAA or EPA and there is anything you don’t understand about this please contact me at and leave me your phone number and I will call you. I know you don’t get it because I have listened to fuel forum CDs from AirVenture and many people make the most outlandish and untrue statements about Mogas and its future in aviation.

Submitted by Dean Billing


  1. Jim Murray says

    Our government has went out of control, not only in this issue of gas, but every facet of American business is now bombarded with new ‘regulations’. Creating new departments that multiply like a virus. In the process science and facts are buried for political gain.

    If the money being spent to subsidize corn were turned toward a real solution it would be here by now.

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