i can’t be the only one who runs regular in a GT right?

[Jstang23]

We can run a full tank of 100 octane on stock engine? Curious to know because a gas station by me has 100 octane and would like to see the difference it makes.

Yup! We sure can! The computer will adjust the timing to handle the higher octane! Altough the difference would be negligible. The main benefit for a engine running 100 octane without a tune is high knock prevention

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[K4fxd]

Curious to know because a gas station by me has 100 octane and would like to see the difference it makes.

Make sure it is unleaded

 

[tcman54]

Try diesel for the extra smokey smell.

 

[ice445]

Remember, "long term" to Ford is only though the end of the warranty period. Yes the PCM will save the engine with the factory calibration, but not forever. Everytime the PCM has to "save" the engine, it means something detrimental (knock) went on in the combustion chamber and it had to intervene. That knock happening over and over again thing does add up over the life of the engine.

For most people that only keep the car a few years and have warranty, no it's not something to worry about. But for those who plan on keeping the car years and years and expecting it to last tens of thousands of miles while constantly knocking is not a smart thing to do.

I agree that in an ideal world, you want the least amount of knock possible. The problem is that the car's PCM logic is always to find the edge of knock, so there's ALWAYS knock. Unless your fuel is so good that you can run borderline + 10 degrees in all circumstances, the PCM is going to find knock and then back off. In a 91+ octane scenario, this means you'll have super minor amounts of knock and then the PCM wll back off slightly. With lower octane fuels, there's the possibility for more severe knock events that necessitate more timing retard. These can be damaging, but often aren't, especially at part throttle where cylinder pressures are lower. It's not ideal to run into it, but the PCM reacts so fast that you usually don't have the thermal runaway effects. Especially since the stock tune uses per cylinder knock sensing at part throttle and low RPM, and then switches to global at higher RPM for more safety.

The thing that's interesting to me about running 87 on these gen 3 cars, is that for some reason, Ford chose not to use the learned octane feature that the ECM supports. It's just not turned on. It's turned on with every single ecoboost platform, since cylinder pressures with boost can get a lot higher and there's more risk. This fact alone tells me that Ford is pretty confident the ECM will intervene quickly enough to avoid damage. Either from timing retard, extra fuel or some combination of the two. Does that mean you can use 87 octane on track days? Yes. Would I personally? No, because the extra heat from a track day will turn the car into doodoo after all the safeties stack on, at the very least. But this is also the one situation where you could actually cause damage by depleting all the safety margin, since you're stacking high CHT/IAT and constant full throttle application on top of the minimum octane. But even then, most drivers probably aren't fast enough to break anything, lol.

 

[Bulldog9]

87 is fine for normal day to day driving, commuting and highway duty unless every stop light is a drag race and every turn is a road course to you. Most important is to use high quality name brand fuel. Road Course/Track, etc? Run 91 or 93. Motor will make optimum power and reduced pinging as the motor heats up. https://www.steeda.com/87-vs-93-octane-for-mustang

I've run both, and for normal driving I can't tell the difference. One of the many reasons I went with my 2020 Bullitt was the ability to run 87.

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