Can you run the Fiesta ST 1.6L on Regular 87 Octane?

[RBYM]

Can you run the Fiesta ST 1.6L on 87 octane and go full throttle safely? In CA all we have is a maximum of 91 octane but I rarely go full throttle. I just just wondering if it’s safe to go wot on 87 octane?

 

[Grsemky]

Yes factory maps allow 87 at reduced power, however I recommended staying with 91.. I'm in AZ with the same shitty gas and never used less than 91

 

[RBYM]

Yes factory maps allow 87 at reduced power, however I recommended staying with 91.. I'm in AZ with the same shitty gas and never used less than 91

Sweet thank you!

 

[Intuit]

If you're at high elevation, pay attention to the octane. 85 might still be sold as "regular"? If so, avoid it. 87 or higher. Higher elevations being less prone to knock, apply for naturally aspirated engines, but not necessarily for boosted engines.

 

[RBYM]

If you're at high elevation, pay attention to the octane. 85 might still be sold as "regular"? If so, avoid it. 87 or higher. Higher elevations being less prone to knock, apply for naturally aspirated engines, but not necessarily for boosted engines.

We have 87 as regular, we don’t have 85. But thank you!

 

[rallytaff]

I have only used 91 in my 2014 since Day 1.

 

[JAMADOR]

I did 87 for the first handful of tanks. Switched to 93 when I started getting a AFR imbalance CEL. Seemed to help for a few tanks but came back this weekend. Have a pair of new O2 sensors to install when I do the next oil change, along with a new set of plugs.

So far, MPG seems to be about the same between 87 & 93 [28-30]

 

[Snrub]

I run 87 all the time. It makes a bit less power (say 5%), but it's not a huge difference. 91 is 25% more than 87 here - Ontario Canada.

View: https://youtu.be/oYsZFu3pmIA?si=P2CxmHpqt2k47Vnt

 

[Intuit]

Personally, I want that 5% and then some. 😅 Senseless... I know...

Hotter engines (ambient temps) tend to need more octane. For the warmer Summer months especially, there may be notably more performance reduction due to increased knock.

 

[Snrub]

I'd be willing to pay it if there was more of a reward.

 

[Capri to ST]

I also want all the power the engine has to give. I'm running the Mountune MP215 tune as my signature says and that actually requires 93 octane, but I would run it anyway. I just think it's a shame to have a high performance car and then hamper its performance by putting in lower octane gas and making it pull power.
The higher octane gas generally has more detergent additives too, keeping everything cleaner, that would be a secondary reason to use it.
The owner's manual is kind of confusing on octane. In one place it says 87 octane is allowed, but in another place when it gives the horsepower and torque ratings it specifies that they are on premium 93 octane gas. What I get from that is that you can use 87 octane, and that you should then be able to go WOT safely with that, but the engine is making less power.

 

[jmrtsus]

2 things, first if you have a Mountune MP-215 the Shell 93 does not play well with our local mix. Randy at Mountune confirmed he had trouble with Shell 93 on the MP-215 tune. Mine runs best on 93 no alky and a station with it is only 3 miles away. Second, on my MP-215 87 octane will run, badly, sluggish throttle response and SLOW. I bought my ST/Mountune for performance first not economy, 37-38 hwy is the norm with 93 for me and way more than expected. Same with our Coyote Mustang.....it will run on 87, slowly! 87 octane is emergency only for us. On the road where 91 is the norm I cannot perceive any change over 93 performance and would run it if we had it.

 

[SteveS]

Higher octane gas does not contain more detergents. The amount of detergent additives beyond the required minimum depends on the vendor. Some have Top Tier designation, which specifies a certain higher amount of detergents, and some go beyond that. The Conoco/Phillips that we almost exclusively use in the Fiesta ST has several times more than the Top Tier standard, even in the 87 octane which we generally use. The vast majority of the driving the car gets is going back and forth to work for my wife. There is no performance driving on that slog. Occasionally we take the car on my weekly trip to go take care of my elderly mother, which involves a 125 mile drive on primarily winding, hilly two lane state and county highways. There is no place on that drive where I miss having premium fuel in the car. I'm already maintaining superlegal speeds and the limit of safe speeds for the road. I'm not drag racing. Why waste the money paying for premium fuel?

I have on occasion bought premium fuel for the car and you cannot really feel any difference. Maybe with a stopwatch you might find a tenth or two of a second difference in acceleration. Immaterial for road driving. And the manual is clear that 87 octane regular is safe for the car. The only place it specifies premium fuel is on the engine specs where it tells you what the power and torque ratings are. They obviously want to protect themselves from someone not getting the max possible power rating (while using 87 octane) by making the necessary statement of what octane fuel is used to measure the power.

 

[Capri to ST]

At least for the Exxon gas that I use, because it is the most convenient Top Tier gas near me, it does have more detergent. They say they added a special one for GDI engines like ours. This is a quote from Exxon's website-

"Synergy Supreme+ premium gas provides enhanced wear protection, better gas mileage, better engine protection and better engine responsiveness.** We added an additional detergent designed for Gasoline Direct Injection engines and upped the ante with product testing that goes above and beyond our traditional benchmarks."