My guess would be that modern automobiles with closed loop feedback engine controls are able to adjust automatically to fuels of different octanes and energy densities.
I probably see no difference between oxygenated E10 and non-E10 because my car was tuned on E10, however inexpertly. Possibly its ultimate potential, perfectly tuned is limited, I don’t know. But it runs well and my fuel mileage doesn’t seem out of line with other owners’ reports.
The reverse might be true if someone tuned their E-type for non-E10 and then put E10 in.
Chris,
Yes, my car does have the insulating blocks between the carburetors and the manifold.
And that’s important. As mentioned elsewhere in this forum, those blocks were added to the original design to prevent “vapor lock” which results when the carb and the float bowl bodies get hot enough to boil the fuel before it gets into the engine. In the case of ethanol fuel I think that the fuel boiling point is lowered enough so that there is boiling even with the insulating blocks present. But apparently it’s marginal- it only happens when underhood temperatures get unusually high, as from very high air temps, or when I drive the car at a heavy load for an extended time, which I experienced several times in going up to the NC mountains.
I might also add that I rebuilt and improved my cooling system when I did all the other work so, yes, the operating temp does go up in those extreme conditions, but it never comes close to overheating- I rarely see temps of 90C.
Whatever the cause, ethanol-free fuel eliminated the the problem.