How much feul efficiency is lost in oldish cars running on E10?

Question

E10 is 90% Gasoline and 10% Ethanol.

I read that:

"If normal automobiles can go more miles on 9 tenths of a gallon of pure gasoline, than they can on 1 gallon of E10 made up of 10% ethanol and 90% gasoline, then forcing E10 ethanol on all customers is the ultimate scam. Taxpayers are forced to put 10% ethanol in their fuel only to realize a 10% to 20% net loss in fuel mileage!"

Is this statement true? Do 'normal' car's receive that much of a decrease in fuel efficiency? I can't find any references.

What is the expected fuel economy loss in lets say a 7 year old car? (or a 'X' year old car where X is the average age of cars driven in the USA.)

Answer 1

As a matter of energy content (after combustion), gasoline contains about 116,000 BTU per gallon, and ethanol contains about 76,000 BTU per gallon.  So a gallon of E10 would contain about,

0.9 * 116,000 BTU + 0.1 * 76,000 BTU = 112,000 BTU

of energy.  This is only 3.5% less energy density than normal gasoline.  So, you could go 116 miles on gasoline, or 112 miles on E10 (100 vs 96.5).  However, that E10 costs about 5% less than the gasoline, so you loose 3.5% range at a savings of 5%, which means you get more miles per dollar.

HOWEVER!!!  There is more to fuel economy than just the energy density of the fuel.  There is the efficiency of the actual combustion to be considered, and it appears that a little bit of ethanol improves that efficiency.  Some recent work has shown that E10 actually gives the same range as straight gasoline, and that ethanol mixtures actually reach peak efficiency (range per BTU) somewhere between E20 and E30.

Answer 2

An older car, one designed for maximum efficiency to operate on gasoline, will experience a 10%-20% reduction in fuel if switched to straight alcohol.   A blend will not see the same reduction.   So let's say the old 1990 pickup gets 10 mpg on gas in theory it would get 8 mpg on ethanol.   Run a 10% blend of ethanol in gas you'll go 9 miles on the gas and an additional .8 miles on the ethanol (actually a little better but let's keep it low ball and easy).   That's 9.8 miles per gallon of the E10.

Reference David Blume 'Alcohol Can Be A Gas' available everywhere but follow the link to Knowledge Publications on my site www.american-renewable-energies.com

Thanks

Answer 3

I doubt that the info is accurate that "normal automobiles can go more miles on 9 tenths of a gallon of pure gasoline, than they can on 1 gallon of E10 made up of 10% ethanol and 90% gasoline"

That would make absolutly no sense and we might as well just be pouring water into the gas.

The loss of efficiency is probably minimal, perhaps around 2 or 4%

Answer 4

Ethanol has 30% less energy by volume than gasoline, IOW a car that gets 10mpg on pure gasoline will get 7mpg on pure ethanol.  A 10% ethanol blend will reduce fuel economy by 3% in ANY vehicle compared to pure gasoline.