Theoretically, anyone with badly maintained equipment will know about it pretty quickly, so the problems should be worked out in a matter of weeks. But keep in mind if the delivery tanker driver isn’t careful with the spill cups after a rainstorm, or someone screws up the ethanol blending process, problems could crop up at any time. If you know about it, I would avoid filling up right after a delivery. also, if a pump runs real slow – that is a sign that the filter in it is plugged (bad maintenance).

I think 89 octane helps because fuel over blended with ethanol will lead to a lean mixture particularly at idle or wot. The 89 helps to make the fuel burn a little faster and thios helps overcome that problem.

And, should we add a fuel additive? Isn’t there one to remove water from the tank? Or am I imagining things?

Gas stations have generally not worried about anywhere up to a couple of inches of water in their tanks because it just sat on the bottom, but ethanol will instantly separate from the gas and can lead to upwards of 10 inches of an alchohol water mix in the tank. The pick up is usually 4-6 inches off the bottom, so this can lead it big trouble ig you happen to pump this into your car.

In addition it is vital that the filters in individual gas pumps at the station be changed once the first load of ethanol blended fuel arrives.

Unfortuanelt many stations may not know when this is, so they won’t have cleaned the tank ensured there is no water and changed the filters.

10% ethanol blended gas should be fine, but there are so many places in the process where trouble can start.

One other: ethanol has to be blended at the distribution terminal (it is too corrosive to be piped with the gas, it must be trucked or rail-shipped). This means that each delivery tanker could theoretically have a different percentage of ethanol depending on how dilligent the person was doing the blending for that load….