Since now, we have flown on car gas 91 Octane more than 300 hours. It is an IO-360 8.5 : 1 Superior with "Airflow Performance Fuel Injection" and "Dual Lightspeed Plasma III Ignition". The FI is approved for 100% Ethanol. The Diaphragm material of the mechanical Fuel Pump is a secret. I will replace the Pump with 500Hours. I added a blast tube to the pump and had never had any problems with vapor or low fuel pressure, even as we crossed the Andes in Peru at 14000ft.
I change the o-ring in the fuel drains every year.
The first 40 hours I used Avgas. Then for a couple of hours Avgas only for LDG/TO and for last 300 hours mostly (95%) car gas 91 Octane or higher if possible.
We used in Brazil car gas with 30-40% Ethanol, with less performance but no problems.
But it is very important to filter the fuel with a very fine filter. I use the "F3C SMALL FUEL/WATER FUNNEL" from AS. The bottom line is, that you can have some very fine, like gum, particles. This gum has no color and is little bit sticky and will block your filter. It is only present if you use ethanol blended car gas.
I will keep posting here every 300hours my further experiences.
In Asia is no Avgas, that means, I can only use car gas.