I run 87 oct in my Fist and its fine :)

[gtx3076]

You won't have any damage running a stock Fiesta ST on 87 octane gas no matter what the temperature is out or how hard you drive. The car is made to handle it.

If you tune it beyond stock, then you are at your tuner's mercy. And if you're tuned, this thread is not for you. You have to then run the fuel that your tuner made the tune for. You have no idea if your tuner built in leeway for lower octane fuel or allowed the ECU to downtune itself to compensate (probably didn't). Even if you run the fuel it was tuned for you might then have trouble if they really pushed the tune.

STkid93 doesn’t know what he’s talking about. You’d think he’d learn a thing or two after all the threads he’s posted.

 

[Stkid93]

@gtx3076

I never claimed to know about tuning. I simply said what I do. are you saying you would run 87 octane on a tuned fist where the tune is designed for 93 octane?

Even stock it’s stupid in my opinion. And again that’s just my opinion. I never claimed to know more than the engineers.. I’m just saying what I would do. I believe Every turbo car should be given 93 octane and synthetic oil. As it runs way hotter than an NA motor. I made that very clear multiple times. And yes I do realize I have posted a lot of threads. But isn’t that what a forum is made for? Other than maybe being slightly annoying I don’t really see what the problem is. Maybe that’s my problem. I see a forum as an open space where people can learn with other people who have the same car, without being attacked for asking questions. Maybe that’s just not how the world is today, everyone is so angry and quick to judge and attack people over nothing. If me posting on a forum is your biggest problem. You have a pretty amazing life. In any case I’m sorry if I lead anyone to believe I am the end all be all of fists because I’m not.

 

[SteveS]

I see a forum as an open space where people can learn

So learn. The car was built by Ford to run on regular unleaded without causing damage. It was designed to use semisynthetic oil without causing damage.

If you run 87 octane fuel the car will make less power than the rated power. If you run 91 octane fuel it will make the full rated power.

Take a look at page 10 of your Fiesta ST Supplement to the owner's manual.

FUEL QUALITY
Use only unleaded gasoline or unleaded
gasoline blended with a maximum of 15
percent ethanol in your gasoline vehicle.
Do not use:
• Fuels containing more than 15 percent
ethanol or E-85 fuel.
• Fuels containing methanol.
• Fuels containing metallic based
additives, including manganese-based
compounds.
• Fuels containing the octane booster
additive, methylcyclopentadienyl
manganese tricarbonyl.
• Leaded fuel. The use of leaded fuel is
prohibited by law.
Note: The use of any fuel other than the
recommended fuel can cause powertrain
damage, impair the emission control system
or cause loss of vehicle performance and
repairs may not be covered under warranty.
OCTANE RECOMMENDATIONS
Regular unleaded gasoline with a pump
(R+M)/2 octane rating of 87 is
recommended. Some stations offer fuels
posted as Regular with an octane rating
below 87, particularly in high altitude areas.
Fuels with octane levels below 87 are not
recommended. Premium fuel will provide
improved performance and is
recommended for severe duty usage such
as trailer tow.

 

[Stkid93]

That’s the thing I am learning, but when people put words in my mouth it’s kinda tough. I never claimed to know better than the designers. All I said is what I do in my own car. And what I think is best. Yes, the car will run perfectly fine on 87 I never debated that fact. All I said, is that i would be afraid to do that in my own car, because lots of things are “okay to do until they aren’t”

Drinking is a perfect example, it’s perfectly okay to drink. But you can’t show up to work drunk. So drinking is okay. Until it’s not okay. So, one person may go 200k miles running 87, while another person blows up their motor after 10k miles. There’s no telling which scenario may happen to you. It’s a gamble. At least that’s my opinion on the topic. And again, I’m probably wrong. That’s just how I feel. So, if anyone out there is listening to what I’m saying, don’t take it as gospel. There are far more knowledgeable people out there on this topic. I’m simply saying what I choose to do with my own car.

 

[CSM]

The ECU on these cars will see the lower knock resistance on 87 octane and will adjust the fuel trimming parameters, which results in lower power due to timing changes along the OEM map. Same thing with higher knock resistant fuels like 93 - fuel trimming is altered over the long term and will result in power increases. In fact, you can run E30 in the OEM ECU and it will make even more torque over 93. A forum member years ago posted dyno runs showing this.

The bottom line, the car is designed to run off 87. perfectly fine to do so.

 

[sonicmn]

That’s the thing I am learning, but when people put words in my mouth it’s kinda tough. I never claimed to know better than the designers. All I said is what I do in my own car. And what I think is best. Yes, the car will run perfectly fine on 87 I never debated that fact. All I said, is that i would be afraid to do that in my own car, because lots of things are “okay to do until they aren’t”

Drinking is a perfect example, it’s perfectly okay to drink. But you can’t show up to work drunk. So drinking is okay. Until it’s not okay. So, one person may go 200k miles running 87, while another person blows up their motor after 10k miles. There’s no telling which scenario may happen to you. It’s a gamble. At least that’s my opinion on the topic. And again, I’m probably wrong. That’s just how I feel. So, if anyone out there is listening to what I’m saying, don’t take it as gospel. There are far more knowledgeable people out there on this topic. I’m simply saying what I choose to do with my own car.

Hey Stkid-

One more tidbit for ya, other than the factory tune, the FiST motor is the same (all part numbers match) to the 1.6T that came in the Ford Escapes/Lincolns, I personally have no issues running 87 in my car most of the time for the last 78K miles only running 91 for track days/autocross for a tank before to get the octane back up.

I understand what your saying about concerns with possible issues and unknowns, but the entire system was pulled out of a high volume production car designed to run 87.

All that said, I do notice a slight difference in power when it runs on 91 which is pretty cool how well it can self tune for octane rating.

 

[Capri to ST]

It's clear that it's safe to run the car on 87 octane, as the comments in this thread and the information from Ford linked above make clear. However, I just can't understand why anyone would choose to do this, I want the car to be able to make the maximum power that it's capable of, and it's also clear that running the car on 87 octane prevents this from happening.
If you're just daily driving it it may not make much difference, but what about that fun time when you can get on it, or when you're merging on to an interstate and it helps to have maximum power? I just don't think it's worth handicapping the power of the car to save $5 or $6 per tank full, but obviously everybody gets to make their own choice here.
I do think it's misleading the way Ford presents their different octane recommendations in different parts of the manual. In the section of the manual referenced above it clearly recommends 87 octane but in a separate section where it lists the power specifications of the car, it clearly notes that that power is only made on 93 octane, screenshot below.

 

[CSM]

People do it for economy reasons. If you're going on a road trip for 2,000 miles, it may make financial sense to just do your fill ups on 87 since it effectively will have the same fuel efficiency as 93

 

[sonicmn]

It's clear that it's safe to run the car on 87 octane, as the comments in this thread and the information from Ford linked above make clear. However, I just can't understand why anyone would choose to do this, I want the car to be able to make the maximum power that it's capable of, and it's also clear that running the car on 87 octane prevents this from happening.
If you're just daily driving it it may not make much difference, but what about that fun time when you can get on it, or when you're merging on to an interstate and it helps to have maximum power? I just don't think it's worth handicapping the power of the car to save $5 or $6 per tank full, but obviously everybody gets to make their own choice here.
I do think it's misleading the way Ford presents their different octane recommendations in different parts of the manual. In the section of the manual referenced above it clearly recommends 87 octane but in a separate section where it lists the power specifications of the car, it clearly notes that that power is only made on 93 octane, screenshot below.

View attachment 60034

I personally do it for $ savings most of the time, I get on the hiway and just cruise to/from work, especially in the winter in MN on winter tires, there isn't enough traction to deal with the torque on 87, and it's only worse on 91/93. The car gets a bit squirrely WOT through 2nd, so why bother in my mind unless I'm expecting to want to go fast.

 

[Capri to ST]

I personally do it for $ savings most of the time, I get on the hiway and just cruise to/from work, especially in the winter in MN on winter tires, there isn't enough traction to deal with the torque on 87, and it's only worse on 91/93. The car gets a bit squirrely WOT through 2nd, so why bother in my mind unless I'm expecting to want to go fast.

That makes complete sense. It's a scenario I hadn't thought of, because it doesn't happen down here. It's a lot warmer and snows very rarely, so I have not gotten winter tires.

 

[SteveS]

You really do not lose all the fun, nor all the speed, with the use of 87 octane. It's still more than enough power to blend with traffic, pass cars on two-lanes, squirt away from stop signs at the limit of traction, and bomb the curves on mountain roads.

Currently at our best-priced local station 87 octane is 57 cents less than 93 octane (Conoco). So for the average 10-ish gallon fillup that's a difference of $6 or so every fillup. 26 fillups a year for a light driver and you're talking about $156. Heavy driver maybe $300. That's enough for a tire or two each year. Or maybe motor mounts or a catch can.

 

[Intuit]

It's clear that it's safe to run the car on 87 octane, as the comments in this thread and the information from Ford linked above make clear. However, I just can't understand why anyone would choose to do this, I want the car to be able to make the maximum power that it's capable of, and it's also clear that running the car on 87 octane prevents this from happening.
If you're just daily driving it it may not make much difference, but what about that fun time when you can get on it, or when you're merging on to an interstate and it helps to have maximum power? I just don't think it's worth handicapping the power of the car to save $5 or $6 per tank full, but obviously everybody gets to make their own choice here.
I do think it's misleading the way Ford presents their different octane recommendations in different parts of the manual. In the section of the manual referenced above it clearly recommends 87 octane but in a separate section where it lists the power specifications of the car, it clearly notes that that power is only made on 93 octane, screenshot below.

View attachment 60034

I was looking for that. For whatever reason the search for the word "octane" or number "93" did not land on this.

For those saying you can't use the torque, 215/45R17 mostly covers that. The Continental ExtremeContact DWS 06 Plus XL takes care of the spinnies... in part because it's a heavy tire but also because of the excellent traction. (wears fast)

 

[jmrtsus]

My 2 cents on this.........My 2016 MP-215 will "run" on 87........but not worth a damn. There is a delay every time I floor it on 87 (like the engine is saying WTF!) and why Mountune says 93 if you want the power you paid for. Nowhere in my list of wants in the FiST was the term "runs on 87 octane", that part of the Manual was normal Fiesta info, the FiST supplement is where you go for FiST specific info. If you and your car are happy with the performance on 87 go for it. I'll stick to 93 non-ethanol when I can get it, easy at home but not so easy traveling. The price is irreverent in our Fist or Coyote, just part of the cost to own to us. As our DD we fill up the FiST about once a month and my wifes Coyote only rarely unless using it as a true GT travelling with a Hi-po cruiser with every option available on her GT/CS, true Grand Touring style. Did over 9k miles on road trips last summer. My FiST saw the dealer one time for warranty to replace a blend door and Sync 3 (non-nav) replacement. '19 Mustang has never seen a Ford dealer nor has my daughters '17 FiST or her mothers Eco-boost '19 Escape. Love our Fords!

FiST On!

 

[Clint Beastwood]

You really do not lose all the fun, nor all the speed, with the use of 87 octane. It's still more than enough power to blend with traffic, pass cars on two-lanes, squirt away from stop signs at the limit of traction, and bomb the curves on mountain roads.

Currently at our best-priced local station 87 octane is 57 cents less than 93 octane (Conoco). So for the average 10-ish gallon fillup that's a difference of $6 or so every fillup. 26 fillups a year for a light driver and you're talking about $156. Heavy driver maybe $300. That's enough for a tire or two each year. Or maybe motor mounts or a catch can.

It just makes the car feel "sleepy" when it's on 87. Everything just feels a bit more lazy.

 

[Clint Beastwood]

That’s the thing I am learning, but when people put words in my mouth it’s kinda tough. I never claimed to know better than the designers. All I said is what I do in my own car. And what I think is best. Yes, the car will run perfectly fine on 87 I never debated that fact. All I said, is that i would be afraid to do that in my own car, because lots of things are “okay to do until they aren’t”

Drinking is a perfect example, it’s perfectly okay to drink. But you can’t show up to work drunk. So drinking is okay. Until it’s not okay. So, one person may go 200k miles running 87, while another person blows up their motor after 10k miles. There’s no telling which scenario may happen to you. It’s a gamble. At least that’s my opinion on the topic. And again, I’m probably wrong. That’s just how I feel. So, if anyone out there is listening to what I’m saying, don’t take it as gospel. There are far more knowledgeable people out there on this topic. I’m simply saying what I choose to do with my own car.

That analogy is dead on arrival - if it were equivalent, then being drunk at work would be the expected baseline, with sobriety as the "improved performance". There is no need for an analogy here, and there's no need for an opinion - the facts are clearly evident and laid out by the manufacturer.

This only pertains to a FiST running a stock tune: The car is engineered to run fine on 87. It is also engineered to give a little "more" on higher octane. The base, expected duty cycle for the engine is 87 octane, and the FiST drivetrain has been through millions of miles of actual and simulated duty cycling prior to the first one rolling off the lot and into a new owner's hands. Ford would not give owners permission to run 87 octane in the documentation included with the vehicle if there was any chance of causing damage, as any damage caused would open Ford up to costly lawsuits from the resulting damage. There is no room for quantitative opinions on a subject that is qualitatively documented.

At the end of the day, the car is fine on 87 octane, but it does dull inputs, responses, and peak outputs as a result. That is the impact. That is the end result. There is nothing else.