I came across an article in the USA Today archive recently. It compares the prices of bio-ethanol to normal petrol and in particular to diesel.
I had originally planned to buy a diesel car before I found out about bio-ethanol. I wanted the cheaper fuel and the ability to drive further on one tank of it.
But in Germany, diesel cars are taxed more. So unless you manage a certain amount of kilometers each year, the saving on the fuel is cancelled out by the higher tax.
These days, diesel drivers are unhappy that the price of their fuel has almost matched that of normal petrol, making it bizarrely more expensive to drive a diesel car than a petrol one. The only benefit is the distance that you can get without having to fill up again.
Since I tend not to drive long distances with my bio-ethanol car, it looks like I took the right decision after all.