Thanks. That makes sense to me. When I used to work for NY State, we would use cars from the state fleet when on official business. Many of these cars were flex fuel Impalas. We were instructed to always use ethanol when available and of course to bring the vehicle back topped off for the next user. There were no special instructions about mixing E85 with gasoline. Thanks again for your reply.
The owners manual for my 2010 Mercury Grand Marquis says to avoid mixing E85 and regular gasoline. It says not to add less than 5 gallons of E85 at one time and not to switch back and forth between gasoline and E85. I like to use ethanol as much as possible but it is not always feasible since there is only on E85 station in my area. I hate to go against the owners manual, but I always thought that a FFV could run on any combination of E85 and gasoline. Has anyone had any adverse effects from switching back and forth between the two fuels? I don't know if GM and Chrysler have similar warnings about E85. Thanks.