Archive for August, 2009


Mythbusters: E10 Reduces Our Dependence On Foreign Oil

August 10, 2009

It has been said over and over, ad infinitem, “E10 reduces our dependence on foreign oil.”  That should be ad nauseum, because there is no evidence whatsoever that it does or has.  It was stated repeatedly by the ethanol lobby and the ethanol booster politicians in Oregon in 2007 when the state passed its mandatory E10 law.  Strangely nobody questioned the premise, they still don’t, even after there was widespread anecdotal evidence right after implementation of E10 statewide, that it wasn’t true, or at the very least wasn’t provable.


Go ahead Google all you want.  Nobody has ever done one.  Oregon sure as heck didn’t do one.

And this is the key problem.  It appears that a lot of cars see mileage decreases in excess of the predicted 1 – 3% that all of the ethanol boosters say should happen.  If it did then they could rightly claim that E10 is reducing gasoline usage by maybe 7%.  But drivers are reporting mileage losses in excess of 10%, sometimes more than 30%.  If that is the case we may actually be using more gasoline under our mandatory E10 program than before the program.  So much for reducing our dependence on foreign oil.

So why could this be happening?  There is a very probable explanation, perhaps somewhat complicated, but it makes sense.  It dates back to the technology used by car manufacturers to meet the U.S. Clean Air Act requirements for 1981.  The new cars switched to sophisticated computer controlled electronic fuel injection systems.  Since that time there have been a number of versions of the fuel control and pollution control systems, the latest being Technology Class 5 vehicles manufactured from 1996 on, which are classified as Low Emission Vehicles (LEVs).  These hi-tech engine control units (ECUs or PCMs) are software programmed to control fuel injection and timing to provide optimum engine operation while minimizing tail pipe pollution levels in conjunction with pollution control devices such as the catalytic converter.  However the software algorithms and adaptive range capabilities for dealing with gasoline additives, such as ethanol, are proprietary.

Before 2006 there were no states with mandatory E10 laws and the highest ethanol blending levels were about 3% for certain areas with winter CO air quality problems.  It is doubtful that any of the ECUs had parameter tables, called fuel maps, that understood what was going on when 10% ethanol was put in the gas tank with its vastly increased oxygen level.

According to this old report, (read the Technical Issues Section starting on Page 3), different ECUs may produce different results on higher ethanol blends.  In fact the latest ECUs may be programmed for very narrow oxygen bands:

“In certain vehicles, the oxygen sensor could have a limited ability to transmit voltage, and could be unable to transmit voltage levels commensurate with the level of oxygen present in the fuel (Cagle 1999).
NOx emissions may be elevated due to the PCM’s inability to compensate for higher oxygen levels. The argument further maintains that ULEVs and other future technology vehicles will require an air/fuel trim within a very tight range to achieve emissions compliance.”

It is doubtful then that any ECUs, or PCMs, built before 2006 have fuel maps that take into account 10% ethanol in fuel.  The report also states that the problems may be worse for earlier versions of ECU / pollution control systems.

Is this why many cars are seeing a much worse mileage decrease than is predicted by the 3% loss of energy in a 10% ethanol blend?