E85 - Fuel Economy

Fuel Economy

Ethanol promoters contend that automotive manufacturers currently fail to equal the fuel economy of gasoline because they fail to take advantages of characteristics which are superior in ethanol-based fuel blends. (Footnotes 19,20). They claim that some ethanol engines have already produced 22% more miles per gallon than identical gasoline engines (Footnote 19). Critics of flex-fuel vehicles say that they fail to match gasoline fuel economy because flex-fuel vehicles are inadequate, not because E85 cannot deliver as much fuel economy.

Ethanol promoters claim that today's flex-fuel vehicles are much too inexact in measuring the ethanol content because car companies will not pay the high patent royalties demanded for fuel content sensors. They state that some flex-fuel vehicles have used wastefully high-flow fuel injectors which are not necessary and waste fuel all the time on either fuel. They state that flex-fuel systems also spray too much E85, and waste fuel in consequence. The technical term is "excessive fuel pulse width modulation". Other ethanol advocates also state that it is a mistake to base ethanol engine design on gasoline engine design, but that ethanol engines should be based on diesel engine design parameters instead. Using this approach, the EPA has produced an ethanol-only engine which achieves much higher brake thermal efficiency levels than gasoline engines achieve (Footnote 21).

In contrast, ethanol critics contest the benefits of E85 by focusing on the fact that E85 has 33% less energy content than "pure" gasoline (and 30% less than the E10 gasohol blend that is sold by almost all retailers in the US). Depending on the vehicle, this can result in a notable reduction in fuel economy and means that, in factory-made flex-fuel vehicles, while E85 is cheaper than gasoline per gallon, per mile it is far more expensive.

If ethanol advocates (Footnotes 19,20,21) are correct, many flex-fuel vehicles fail to equal the mileage of gasoline-only engines because they do not preheat ethanol-blend fuels, or radically advance ignition timing for those fuels, or increase engine compression for E85 fuel,not because E85 contains less energy than gasoline. fuel economy is reduced for most factory-made FFVs (flexible-fuel vehicles) by about 20 to 30% when operated on E85 (summer blend). The Environmental Protection Agency states on its website that several of the most current factory-made FFVs are still losing 25% fuel efficiency when running on E85.

For factory-made FFVs, more E85 is typically needed to do the same work as can be achieved with a lesser volume of gasoline. This difference is sometimes offset by the lower cost of the E85 fuel, depending on E85's current price discount relative to the current price of gasoline. As described earlier, the best thing for drivers to do is to record fuel usage with both fuels and calculate cost/distance for them. Only by doing that can the end-user economy of the two fuels be compared. For example, an existing pre-2003-model-year American-made FFV vehicle that normally achieves, say, 30 MPG on pure gasoline will typically achieve about 22 MPG, or slightly better, on E85 (summer blend.) When operated on E85 winter blend, which is actually E70 (70% ethanol, 30% gasoline), fuel economy will be higher than when operating on the summer blend.

To achieve any short-term operational fuel-cost savings, the price of E85 should therefore be 20% or more below the price of gasoline to equalize short term fuel costs for most older pre-2003 FFVs for both winter and summer blends of E85, which it typically is. Life-cycle costs over the life of the FFV engine are theoretically lower for E85, as ethanol is a cooler- and-cleaner burning fuel than gasoline. Provided that one takes a long-term life-cycle-operating-cost view, a continuous price discount of 20% to 25% below the cost of gasoline is probably about the break-even point in terms of vehicle life-cycle operating costs for operating most FFVs on E85 exclusively (for summer, spring/fall, and winter blends).

Fuel economy in fuel-injected non-FFVs operating on a mix of E85 and gasoline varies greatly depending on the engine and fuel mix. For a 60:40 blend of gasoline to E85 (summer blend), a typical fuel-economy reduction of around 23.7% resulted in one person's carefully executed experiment with a 1998 Chevrolet S10 pickup with a 2.2L 4-cylinder engine, relative to the fuel economy achieved on pure gasoline. Similarly, for a 50:50 blend of gasoline to E85 (summer blend), a typical fuel-economy reduction of around 25% resulted for the same vehicle. (Fuel-economy performance numbers were measured on a fixed commute of approximately 110 miles (180 km) roundtrip per day, on a predominantly freeway commute, running at a fixed speed (62 mph), with cruise control activated, air conditioning ON, at sea level, with flat terrain, traveling to/from Kennedy Space Center, FL.). It is important to note, however, that if the engine had been specifically tuned for consumption of ethanol (higher compression, different fuel-air mixture, etc.) the mileage would have been much better than the results above. The aforementioned fact leads some to believe that the "FFV" engine is more of an infant technology rather than fully mature.

The amount of reduction in mileage, therefore, is highly dependent upon the particulars of the vehicle design, exact composition of the ethanol-gasoline blend, and state of engine tune (primarily fuel-air mixture and compression ratio). In order to offset this change in fuel economy there has been much legislation passed to subsidize the cost. The American Jobs Creation Act of 2004 created the Volumetric Ethanol Excise Tax Credit (VEETC) to subsidize the production costs. In 2008, the 2008 Farm Bill changed the 51-cent tax credit provided by VEETC to 45-cents. There have been other measures taken by congress to jump start ethanol production. For instance, the 2004 VEETC bill provided for a Small Ethanol Producer Tax Credit which gave tax credits to small ethanol producers. More recently the Tax Relief, Unemployment Insurance Reauthorization, and Job Creation Act of 2010 extended the tax cuts allowed by VEETC that were set to expire at the end of 2010 until the end of 2012.

So in order to save money at the pump with current flex-fuel vehicles available in the United States, the price of E85 must be much lower than gasoline. E85 was at least 20% less expensive in most areas, as recently as 2011. However as of March 2012, the difference in the retail price between E85 and gasoline is 15% or less in the vast majority of the United States. E85 also gets less MPG, at least in flex-fuel vehicles. In one test, a Chevy Tahoe flex-fuel vehicle averaged 18 MPG for gasoline and 13 MPG for E85, or 28% fewer MPG than gasoline. In that test, the cost of gas averaged $3.42, while the cost for E85 averaged $3.09, or 90% of the cost of gasoline. In another test, however, a fleet of Ford Tauruses averaged only about 6% fewer miles per gallon in the ethanol-based vehicles as compared to traditional, gas-powered Tauruses.