Does the EPA test car's with 10% Ethanol

In theory, in general, ethanol has higher octane, but lower energy, by 30% (many premium blends have less energy than regular, they just resist knock better.

So again in theory, in general you would expect a 3% reduction in mileage with 10% ethanol. The various Prius engines, (Gen I to Gen III) may do better or worse than 3%, like all engines. Engines that like higher octanes will do better, but the Gen II has no preference for higher octane. So far as I know, no one has exhaustively tested Gen III.

http://en.wikipedia.org/wiki/Ethanol#As_a_fuel

 

The impression I've had with several vehicles (single tank measurements) is that ethanol mpg loss exceeds 5% and is not compensated for by reduced price.

 

You'd likely not have a large & accurate enough sampling to properly conclude that.

The average for my Prius is 54.3 MPG, despite only using E10 and just driving it.
.

 

In Illinois, where I visit my family, the E10 is cheaper. In upstate New York, where I live, only a few stations have E10 and the price is the same as regular gas.

The last 3 half tanks I had (I was traveling) ended up being E10 and my mileage dropped from 58ish to 53ish. Note that it may have been due to the different driving (almost entirely highway/thruway and a bit hillier vs my normal 50/50 with a few small hills) but I didn't spend time searching for regular gas, just chose the closest stations.

On another note, my latest full tank, purchased at my regular station is yielding in the low 50s on my regular commute. A coworker (Prius II driver) stopped by yesterday and asked if my mileage had dropped in the last week. His did and he thinks that the winter formulations have been started

Robbin

 

The original question is a good one. I would doubt they use E10. Good question though, and one I would like to have the answer too also.

 

Now that it's hard to find 'real' gas anymore, perhaps that's why I only average like 43MPG anymore. It was 50MPG up near Buffalo in August, but now I can't recall what those pumps said. I thought it was the terrain.

Where do you FIND non-E10 gas anymore? I thought the required pollution-reducer they used to use was banned?...

 

Don't know the answer but they use a special blend of gasoline for the test.

Why do you think that owners of any car should necessarily get EPA "benchmark" mileage? See the two links at http://priuschat.com/forums/other-c...uth-about-epa-city-highway-mpg-estimates.html for info about the test.

 

I'm near Rochester and I've only seen a few stations with E10 (Delta Sonic was one, a local Gulf was the other). I usually go to BJ's since the price is good and I was just below 55 calculated MPG (58.x reported)

Robbin