Strictly going by the language used , no. The manual did not say, 'any octane rating above 91 or 93 preferred', or, 'the higher the better'. There maybe good reasons not to go higher, though one would be tempted to do so. One way of using that 110 octane pump is to go just a bit higher than the 91 that is generally available. by running your tank as close to empty as safely possible. Then filling it to say 75%. Then driving to the 110 pump to top it off. That would roughly give you the 93 octane rating that is preferred according to the manual. Even then, you still may not be in the clear: Say you now have a perfect 93 octane averaged. But that doesn't mean that both fuels are perfectly mixed. The higher octane that may be denser would settle to the bottom of the tank. So if the fuel pump is sucking from there (which it should be) the motor would be getting, say 96-100 octane gas, higher than the preferred figure of 93. Perhaps the ecu is programmed to safely scale up its performance to higher than 93, but that you would have to know for sure. There is a good chance that the system, the way it is mapped, will de-tune itself in order to protect itself and will give you worse performance than using 91 octane. This has happened to people with other modern cars. But there other side effects to consider. If the performance increases, seals and vibration sensitive running gear may prematurely fail, as the car is assembled with the stock performance target in mind. Ford dealers will probably cover it under warranty, whether they know you did something or not. But you sure will feel like the cat that ate the canary. Other , less expected, side effects can occur by going higher than preferred 93 octane. This happened with me when fueling using a gas cap-less system, similar to the GT350, on another modern car while playing with a mix using unleaded 100 plus octane available at my local Sinclair. The the fuel nozzle would turn off before the tank would fill. I would have to repeatedly re-squeeze the handlle to let in a small amount of gas in at a time. After two or more weeks of this, I stopped putting the 110 plus octane in, and by the next time I fueled, the problem disappeared permanently! Perhaps the denser fuel turned to a denser than normal vapor creating enough pressure to trick the nozzle sensor that the tank was full. Also, during the time I used 100 plus octane, I did feel more pep. However, it was also during that time, that during a routine oil change, the dealer technicians discovered a leaking turbo oil lubricant line at one of the connectors. The dealer found a failed washer that they claim was defective and replaced it. But I believe that my particular car loved the added juice, revved faster invoked turbo spool a bit faster than the car was set up to do and invoked failure of a defective part that may have not occurred so soon or even ever!Hello all,
Owner's manual says 91 octane minimun, 93 preferred.
Local Sunoco stations carry " racing fuel " at 110 octane.
Worth it-from a performance point of view ?