2018 GT MPG 87 vs. 93 octane

[Gregs24]

Bikeman 315, I think you are wrong. Today's engines advance the timing until they detect detonation and back it off slightly until no more detonation is detected. When they do that (think Digital Fuel Injection and the attendant sensors), then the 87 octane fuel WILL result in less power delivered before detonation is encountered ... IF YOU ARE USING THAT MUCH POWER from your engine.

If you are not, then 87 octane is OK. But if you are making more than around half of the max power output of which the engine is capable, higher octane fuel will result in more power produced and delivered before detonation starts to occur. In this case, the lower octane fuel will be constrained to not detonate by the CPU, but it WILL hurt your possible power produced relative to using better-performing fuel. The CPU may not allow the engine to be damaged, but it will also make less power then it would with better fuel.

A carbureted engine will not run that way, adjusting for detonation. But digital fuel injection will.

Agree

Premium fuels have two significant differences. Higher octane ratings which means more controlled burn and resistance to detonation enabling more advanced ignition and better torque. They also contain better detergent additives.

Standard fuel in a car that can adjust timing for pre-ignition will result in sub-optimal performance, but not cause damage per se.

Pays your money and makes your choice.

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[COVID19]

With the Stock tune. Put in 2gallons of E85 top off with 87
Get a octane inrease above the 87 and still save money.

 

[Hack]

Bikeman 315, I think you are wrong. Today's engines advance the timing until they detect detonation and back it off slightly until no more detonation is detected. When they do that (think Digital Fuel Injection and the attendant sensors), then the 87 octane fuel WILL result in less power delivered before detonation is encountered ... IF YOU ARE USING THAT MUCH POWER from your engine.

If you are not, then 87 octane is OK. But if you are making more than around half of the max power output of which the engine is capable, higher octane fuel will result in more power produced and delivered before detonation starts to occur. In this case, the lower octane fuel will be constrained to not detonate by the CPU, but it WILL hurt your possible power produced relative to using better-performing fuel. The CPU may not allow the engine to be damaged, but it will also make less power then it would with better fuel.

A carbureted engine will not run that way, adjusting for detonation. But digital fuel injection will.

Everything you say is correct. However, in many situations the difference in power is not detectable.

 

[WildHorse]

in many situations the difference in power is not detectable.

Then you ain't trying hard enough. Lug it in 3rd at 2000 rpm with 87 and watch your knock sensors go batshit crazy. Then do the same with 93+.

 

[Bikeman315]

Then you ain't trying hard enough. Lug it in 3rd at 2000 rpm with 87 and watch your knock sensors go batshit crazy. Then do the same with 93+.

And you want to go out and do this, why? Just to prove that you will get better performance from 93 than 87? We already know this. I think most owners running 87 regularly know not to beat in their motor. Those that do, well you can’t fix stupid.

 

[Hack]

Then you ain't trying hard enough. Lug it in 3rd at 2000 rpm with 87 and watch your knock sensors go batshit crazy. Then do the same with 93+.

No. I would never lug the engine in any car I own. Definitely I would never do it deliberately. WutRuNUTS?

And you want to go out and do this, why? Just to prove that you will get better performance from 93 than 87? We already know this. I think most owners running 87 regularly know not to beat in their motor. Those that do, well you can’t fix stupid.

Agreed. If it's hot and you're going to the track, definitely run a higher octane if it's available. Driving on the street and doing a short burst here or there within traffic laws, you won't notice... unless you misuse/abuse your engine in some way.

 

[WildHorse]

No. I would never lug the engine in any car I own. Definitely I would never do it deliberately. WutRuNUTS?

Your knock are doing the same on 87 at WOT. And if you guys say you don't go WOT on 87.. you're fricken lying haha.

 

[Bikeman315]

Your knock are doing the same on 87 at WOT. And if you guys say you don't go WOT on 87.. you're fricken lying haha.

Honestly, at this point I have no idea what you're trying to say. I think we agree that if you are going racing or beating your motor on the street go with 93. For daily/highway driving with the occasional WOT or whatever, 87 will be fine and do no damage to your engine. Do I use 87? No, that's my personal choice. To each his/her own.

 

[Hack]

Your knock are doing the same on 87 at WOT. And if you guys say you don't go WOT on 87.. you're fricken lying haha.

I go WOT with 87 octane in the tank all the time and I have no worries. Ford did a great job on the Coyote. I often ran the Voodoo on 91 - even on track - and never had an issue with that either.

Honestly, at this point I have no idea what you're trying to say. I think we agree that if you are going racing or beating your motor on the street go with 93. For daily/highway driving with the occasional WOT or whatever, 87 will be fine and do no damage to your engine. Do I use 87? No, that's my personal choice. To each his/her own.

I would go with higher octane on the road course if available, but I realize that Ford has built the Coyote to perform fine on 87. I've been to the road course before running 87 because it was what was available where I fueled up. And I had no concerns and no issues. And I have never noticed a power difference. I'm sure you could measure a difference, but it's not a big enough difference for me to notice.

 

[Flyhalf]

In a 12:1 compression engine. Putting 87 is just..wrong.
In racing the 91 is still low and many tuners suggest to go up with few gallons of 100.
My point is.
Can you drive the car to the grocery store with 87? Sure.
Is it optimal. Nope.
Can you rev up on 87? Your risk.
buy a 460hp car to save 5$ for a full tank seems to me a risk you should not take.

 

[Bikeman315]

In a 12:1 compression engine. Putting 87 is just..wrong.
In racing the 91 is still low and many tuners suggest to go up with few gallons of 100.
My point is.
Can you drive the car to the grocery store with 87? Sure.
Is it optimal. Nope.
Can you rev up on 87? Your risk.
buy a 460hp car to save 5$ for a full tank seems to me a risk you should not take.

OK.

 

[WildHorse]

will be fine and do no damage to your engine.

Didn't say anything about damaging the engine. However, 87 is a hotter more violent burn tha 91+, and the knock sensors can only do so much. Just check your logs if you don't believe me. IE: Audible vs silent knock.

 

[Hack]

In a 12:1 compression engine. Putting 87 is just..wrong.
In racing the 91 is still low and many tuners suggest to go up with few gallons of 100.
My point is.
Can you drive the car to the grocery store with 87? Sure.
Is it optimal. Nope.
Can you rev up on 87? Your risk.
buy a 460hp car to save 5$ for a full tank seems to me a risk you should not take.

It's 11 to 1 compression ratio in my Coyote. And Ford recommends 87 for it. If a Coyote engine fails on 87 Ford would warranty it. And if it does fail, I would seriously doubt the octane had anything to do with it. There's no risk there.

I would be a little more nervous about running lower octane on track in a PI/DI Coyote, but if Ford recommends it I'm sure it's ok. The bias against direct injection is a personal thing for me, not that I doubt Ford is doing a good job with designing and testing their engines.

If you are driving a car for personal enjoyment, whether on the street or track, why is spending more on gas optimal? I did try higher octanes many times in previous GTs I've owned. Believe me, if I noticed a difference I would fuel up with the highest octane I could find. I would even go out of my way to find a station that sold it. That's what I did with the GT350 as well before I realized I couldn't tell any performance difference between 93 and 91 in that car.

I think unless you are somehow earning money with the speed of your vehicle it seems foolish to spend more on gas than you have to. You're definitely not extending the life of your vehicle doing it.

 

[Flyhalf]

Sorry. The post said 2018 so is 12:1.
2017 yes is 11:1

 

[ice445]

The car will run fine on 87, Ford did a good job with the knock detection and timing tables in that regard. You WILL lose power especially under back to back runs, hot days, etc. And unfortunately the stock knock detection routine on these cars will pull a LOT of timing and keep it held back for a long time, so I don't know how anyone claims that the car makes the same power on 87 unless they don't ever accelerate, or only use it in the winter or whatever.

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