Fuel

[Gallego1968]

As i haven't owned an ST till now and drove mind numbingly boring cars for a good few years i want to know would the ST run better on higher octane than 91, if so can you feel the difference for the extra cost of the fuel.

 

[TyphoonFiST]

As i haven't owned an ST till now and drove mind numbingly boring cars for a good few years i want to know would the ST run better on higher octane than 91, if so can you feel the difference for the extra cost of the fuel.

You can run it on regular if you want. BUT...Performance suffers. The car will know what kind of fuel you put in it using OAR/ octane adjustment ratio to tell the car to retard the timing. It should always read -1.0... If it senses poor fuel quality it will start trending towards +1.0....not good for performance. I have never put anything but premium in my car....I am NOT A FRUGAL person and want the Best for my FiST. Don't you? If not I'd just save yourself some money and get a regular Fiesta or maybe a Fiesta ST line/ Imposter FiST. Just put premium in it....End of story.

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[SteveS]

Even run on regular unleaded the Fiesta ST is still a night and day difference from the regular Fiesta. If you are doing ordinary daily driving to and from work, grocery shopping, etc., you will not notice any difference between regular unleaded (87) and the 91 or 93 you can pay more for. People have done dyno tests comparing them, and on the first pull the car did the same on either gas. It was only with repeated pulls as the engine heated up that there was a falloff with the 87. Unless your daily commute is the Streets of Willows, you won't be able to tell the difference, and if you can tell the difference, your driver's license is likely suffering. You can still have all the fun of the Fiesta ST and save that 70 cents a gallon.

Now if you are running an aftermarket tune, take your car to the track every weekend, or something like that, the premium makes sense.

 

[Ford ST]

93 all-day everyday. I can tell the difference. I drive hard though.
87 nope not going to happen.

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[lowda9]

I run 91 always. However, when I first test drove the car, the dealer probably had 87 in it and also their "free" full tank of gas after purchase was probably filled with 87. If stock you can run 87, but if get a tune you'll have to run 91 minimum.

 

[smneufell]

I use 93 top tier only too. It's not JUST the performance, but the fact(maybe?) that higher octane gasses generally have more beneficial additives to keep stuff good and clean, unfortunately not as much a factor with DI. Plus, my commutes are mostly town and see lots of load. That and my OCD. I've logged literally 99% of every mile driven over the last 2-3yrs, even with my old car with Torque Pro. OAR is in the list and hasn't veered from -1.0 since ownership, even with my own "self-tune" with raised OAR sensitivity/response. Look at the difference. Daily driving, average acceleration for me is usually around .5-1.0 load. This table is mostly for extreme conditions (hot days), but it gives an example to what fuel quality does. There are a few tables like this one.

And don't forget a good synthetic oil, that also plays a part in OAR to an extent. Low quality oils will mist through the turbo under boost, mix with the intake, and lower the overall octane if they're prone to burning.

 

[Remi]

I use 93 top tier only too. It's not JUST the performance, but the fact(maybe?) that higher octane gasses generally have more beneficial additives to keep stuff good and clean, unfortunately not as much a factor with DI. Plus, my commutes are mostly town and see lots of load. That and my OCD. I've logged literally 99% of every mile driven over the last 2-3yrs, even with my old car with Torque Pro. OAR is in the list and hasn't veered from -1.0 since ownership, even with my own "self-tune" with raised OAR sensitivity/response. Look at the difference. Daily driving, average acceleration for me is usually around .5-1.0 load. This table is mostly for extreme conditions (hot days), but it gives an example to what fuel quality does. There are a few tables like this one. View attachment 26606

And don't forget a good synthetic oil, that also plays a part in OAR to an extent. Low quality oils will mist through the turbo under boost, mix with the intake, and lower the overall octane if they're prone to burning.

Good info. I never thought about using Torque Pro to monitor this.

BTW, I love your disclaimer.

 

[jmrtsus]

93 octane NON ethanol gives my Mountune MP215 better mileage and performance. Ford and Mountune's HP ratings are made using 93 octane-w/ethanol