I found out from the local news the other day that gas stations in North Carolina have been putting a 10% mixture of ethanol in thier tanks. NC laws do not require labeling of the pumps. Would this affect the Miller Cycle engine even though the fuel is rated at 93 octane? I've been having troubles off and on all summer long with idling and an occasional P0300. Apparently they have been doing this for a while.

 

I don't think it would cause a problem (Ethanol is fairly high octane) but it will negatively impact your fuel mileage.