Bob it might help if you let folk know what car model you are talking about.

I can't help with the problem, but would have thought that the ECU etc would be able to handle modern fuel, otherwise we would have a host of links to reprogramming ECU's, which I'm fairly sure we don't.

Hopefully others will help.

 

What year/model?

 

In the Dallas, TX area our gas is "up to 10%" Ethenol (distilled from corn, I think.) Is that the same as the alcohol you mentioned? My 2002 XJ8L 4.00 will run satisfactory on any of the octanes we have locally: 87, 91 and 93, but it has a little more pep with the 93. Not even a tank of 87 octane causes any pinging, though.

Is it possible you have a failing oxygen sensor or some such thing? Any malfunction codes? Just a thought; I don't have personal knowledge to be of specific help.