Originally Posted by gpsman1

There is increasing evidence that E10, or gas with 10% ethanol is the worst possible blend for your car. The 10% is just enough to mess with the fuel, but not enough to get the sensors to "adjust" properly. ( or the reverse, the 10% messes with the sensors to a much greater degree than is called for )

3 recent studies, one by Volvo, one by the University of North Dakota, and one by Minnesota State University all point to a "sweet spot" MPG in most cars using E30, or 30% ethanol.

In the case of the I4 2.3L Ford Fusion, this car got better MPG with 30% than with 100% gasoline. The Ford Fusion did worse than gasoline, but better than predictions based only on btu content, with 20% ethanol.
The Ford Fusion did worse than predictions at 10% ethanol, and blends over 45% ethanol.

The 2.4L Toyota Camry also did better than pure gasoline with 30% ethanol.
The 3.5L Chevy Impala did best on 40% ethanol, nearly as good as pure gas, but not quite.

It seems in modern, newer cars ( the 3 cars tested were all 2007's ) the air/fuel sensors, and fuel injectors adjust "properly" ( or at least to your advantage... the lean side of things ) at about 30-40% ethanol.

NONE of the cars tested got a "check engine" or warning lamp with less than 50% ethanol. Some "regular" cars can run on up to 65% ethanol before getting a check engine lamp. All cars "run" on E85 ( just poorly ).

So myself and some others at work are going to give this a shot.
( most people I know do not drive hybrids though )
We are going to mix our own 30% and 40% ethanol fuel.
It is easy to do if you live in an area where you can get E85.
Just "dilute" the E85 with regular gas.
( or "enrich" your gas with some E85 )

The tables below tell you exactly how to do this.
Table 1 is for E85 and plain gas.
Table 2 is for E85 and E10 gas.

If possible, allow 3 tanks for your car to fully "learn" the new mix, and to average out weather and traffic concerns that affect MPG.
However most researchers feel this adjustment period only takes 30 minutes / miles.
Please report your findings. Thank You. -John