[newgeezer]

It also isn't cheaper when you consider it knocks mi/gal down by about 25%.

If you're talking about a 10% ethanol blend, 25% sounds awfully high.

EPA MPG estimates for E85 (85% ethanol + 15% gasoline) in flexible-fuel vehicles is typically 30% less than for gasoline. Also, ethanol has 30% less BTU (energy) than gasoline.

So, theoretically, if all else is equal, a 10% ethanol-blend should result in a MPG penalty of less than 5% when compared to straight gasoline.

At any rate, a 25% penalty from a 10% blend doesn't sound right to me.

[TFMcGuire]

difference in the energy of the ethyl alcohol molecure as compared with the assorted HC molecules which make up the gasoline mixture.

E-85 would produce the "desired" resuts.

Although, emprically, it does "seem" like 10% C2H5OH knocks mileage of my 2001 Silverado down at least 10% as well.

[TFMcGuire]

I took for granted he meant the E-85.

The 30% reduction in the energy of the molecule translates to a 30% reduction in mileage.

I am convinced, as well. that a 90/10 blend reduces mileage in my Silverado by at least 10%.

And I track my mileage nearly every fillup.

We've experience her in Denver with the 10% blends and I despise them for the reduced mileage.

[mad_as_he$$]

On a hunting trip to South Dakota last year we carefully tracked the mileage on a 2000 Chevy Silverado that had 100,000 miles of mileage data in the book. It consistently, over that time, got exactly 16.5 mpg When we put the 85 in the mileage dropped to 14.2 over 800 miles (two full tanks+ some). Interestingly enough the 87 octane regular in Wyoming kicked it up to 17.1. One vehicle over a 3600 mile test with the same load and tracking the same route both ways.

FWIW I suspect that not just the btu content is at play but the fact that you also "carry" fuel - the weight being a factor - more btu's/lb less tare.