Premium fuel or Regular? GT Coyote V8

[JohnD]

The manual says use regular, so that's what I use

You better watch out, quoting the manual like that. There are many folks in these parts of the internets that believe the manual is just not a good source of information at all. THEY, whoever THEY are, know better, according to THEM.

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[Stormtrooper5.0]

I use that sams club 87 octane on my baby cuz I'm broke.

 

[WildHorse]

You better watch out, quoting the manual like that. There are many folks in these parts of the internets that believe the manual is just not a good source of information at all. THEY, whoever THEY are, know better, according to THEM.

Well according to the manual, that's not the recommended fuel. But whatever floats your boat.

 

[millhouse]

Well according to the manual, that's not the recommended fuel. But whatever floats your boat.

"We recommend regular unleaded gasoline with a pump (R+M)/2 octane rating of 87. Some stations offer fuels posted as regular with an octane rating below 87, particularly in high altitude areas. We do not recommend fuels with an octane rating below 87.
To provide improved performance, we recommend premium fuel for severe duty usage, such as trailer tow."

87 is recommended.

If you want the small amount of extra power and torque (less than ~ 10hp) then by all means, run premium.

 

[WildHorse]

My bad. There ya go. Run 87 all day long. Cheers.

 

[Hashbrownn]

Burn what you can afford.
it's pretty simple

 

[HoosierDaddy]

Burn what you can afford.
it's pretty simple

That's what I used to say.

But then my wife convinced me to use wood instead of paper money in our fireplace.

 

[bootlegger]

"For best overall vehicle and engine performance, premium fuel with an octane rating of 91 or higher is recommended."

The 2018 recommends premium for optimal performance. I can feel the difference. My first tank was 87 (dealer filled) and the second tank is 93. Now, some of that may be ECU learning, but the DIG higher compression engines generally benefit more from higher octane.

 

[jasonstang]

"For best overall vehicle and engine performance, premium fuel with an octane rating of 91 or higher is recommended."

The 2018 recommends premium for optimal performance. I can feel the difference. My first tank was 87 (dealer filled) and the second tank is 93. Now, some of that may be ECU learning, but the DIG higher compression engines generally benefit more from higher octane.

The 18 has higher compression so premium can benefit.
With that being said the PI Coyotes can also benefit from using higher octane gas.

 

[jasonstang]

You better watch out, quoting the manual like that. There are many folks in these parts of the internets that believe the manual is just not a good source of information at all. THEY, whoever THEY are, know better, according to THEM.

The way I look at manuals is that they are minimum requirements. You can get better results using better stuff than what's recommended in the manual.

 

[Zelek]

"For best overall vehicle and engine performance, premium fuel with an octane rating of 91 or higher is recommended."

The 2018 recommends premium for optimal performance. I can feel the difference. My first tank was 87 (dealer filled) and the second tank is 93. Now, some of that may be ECU learning, but the DIG higher compression engines generally benefit more from higher octane.

That's not technically true. It has to do with the timing advance the ECU does. My other car is a high compression engine and runs on 87 octane. 93 does nothing different for it, same MPG, same horsepower, 13:1 compression ratio.

This is why tuning the car makes such a huge difference with fuel because you can advice the timing so much more on 93 than 87. The stock tune doesn't advance the timing near as much as it can. It does slightly, but not near as much as it should.

 

[bootlegger]

That's not technically true. It has to do with the timing advance the ECU does. My other car is a high compression engine and runs on 87 octane. 93 does nothing different for it, same MPG, same horsepower, 13:1 compression ratio.

This is why tuning the car makes such a huge difference with fuel because you can advice the timing so much more on 93 than 87. The stock tune doesn't advance the timing near as much as it can.

Of course timing has something to do with it. However, higher compression engines need to back off the timing more when running low octane fuel to prevent detonation. The Mustang is tuned from Ford using premium fuel. This is why all HP ratings have a note mentioning the fuel used. When you use 87, especially in the 2018 GT, the ECU backs off timing to compensate. This will in turn reduce power.
In some cars, there is no ecu logic to advance timing for the increased octane. In those cases, running premium does nothing. The Mustang is not one of those cars. I have had these discussions many times after working in the petrochemical industry. Running 87 won't hurt the Mustang. However, you should expect power loss across the board. Personally, I run 93, but not just for the optimal power. There are other benefits, like increased detergency and friction modifiers, that you get with the premium top tier fuels (Shell, ExMo, BP).

 

[Zelek]

Of course timing has something to do with it. However, higher compression engines need to back off the timing more when running low octane fuel to prevent detonation. The Mustang is tuned from Ford using premium fuel. This is why all HP ratings have a note mentioning the fuel used. When you use 87, especially in the 2018 GT, the ECU backs off timing to compensate. This will in turn reduce power.
In some cars, there is no ecu logic to advance timing for the increased octane. In those cases, running premium does nothing. The Mustang is not one of those cars. I have had these discussions many times after working in the petrochemical industry. Running 87 won't hurt the Mustang. However, you should expect power loss across the board. Personally, I run 93, but not just for the optimal power. There are other benefits, like increased detergency and friction modifiers, that you get with the premium top tier fuels (Shell, ExMo, BP).

Yeah, I wouldn't put anything less in the Mustang either. High horsepower V8 versus a little 4 cylinder with high compression are two different things. I'd be interested to see the knock sensor on someone running 87 octane at WOT.

I still put 93 in my Mustang before I was tuned just because that's what I've always been familiar with even in my F-body days.

 

[Hack]

On a hot day you might notice a difference between 87 and 91. When it's below 60 degrees you won't.

 

[Olivas]

This is always as good as the oil debate.

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