PREMIUM-VS-REGULAR GAS FOR 2024 GT??

[AZ_Ryan]

The HP difference is an interesting question for sure. I seem to remember seeing some factory dyno numbers using different octains on either the gen 2 or gen 3 a few years back. Obviously the gen 4 has a bit higher compression, but im sure it's comparable. I'll see if I can find it...

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[MAT1955]

@AZ_Ryan I have modified my post to be more respectful, as I should be. IMO knock sensors for adaptive timing (even self retarding variable camshaft timing) that detect "ping" pre detonation etc. are often referred to as "oh shit" meters because by the time the detection and retardation are done so has some amount of damage. There is always a lag. They are meant for a serious one or two times problem not intended to constantly correct for low octane gas. Under that condition cumulative damage will occur. What mystifies me is that - unless I am totally wrong - most of the forum members are not one pay check away from a mortgage foreclosure.....so why would we discuss if we can use cheaper gas and oil when both are so critical to these, arguably, high performance engine's performance and longevity. It seems to me to be penny wise and dollar foolish. I have held, many times, pistons and seen cylinder sleeves subjected to pre-detonation, run on etc. They were from significantly damaged engines.

 

[AZ_Ryan]

@AZ_Ryan ..... in case you are talking with any engine builders - to save you embarrassment - knock sensors for adaptive timing that detect "ping" pre detonation etc. is referred to as an "oh shit" meter as by the time the detection and retardation is done so has some amount of damage. Every time. As family would say anyone relying on their engine to solve crap gas by retarding the engine is a retard. Running the 2024 and up GTs on low octane gas to save a few pennies is IMO a real cheap, dumba$$ move and indicates someone who doesn't know what they are talking about and certainly doesn't deserve a HP engine. Yeah, LOL.

I'm not talking about knock sensors. I'm talking about independent variable camshaft timing.

And while I dont agree with using lower octane either, I do think the OP brought up a good and interesting topic and still diserves his car lol. But something tells me you aren't going to be capable of a civil conversation on this. Try not to bust a vein typing back.

 

[ZXMustang]

It’s not about “less hp”, it’s about the car detonating or pre ignition knock and pulling timing to make less hp.

93 octane is hardly adequate, it’s a 12:1 high comp engine…

people gain more adding in a gallon or 2 of E85 from the extra octane and computer adapting.

This. I run e30 in mine, but its a pure pleasure car. I've datalogged it with E30 and its adding about 15% on average of fuel volume to keep stoich. So its well within the fuel system limits to be able to sustain the e30, and I'm not getting a hint of KR anywhere at any RPM or load with it. 93 was fine, but I was seeing KR here and there, so the car was suffering for sure at times.

 

[young at heart]

Washington state has the 3rd highest average gas prices in the USA, right behind California and Hawaii!….I know, I paid for the GT’s HP, so why not get it all the time, right? How much HP is lost if I used 87 octane? Premium here is 50 to 60 cents more per gallon and it hurts, just a little each fill up, you know?

I’m sure you were aware of everything you mention before you bought the car, so perhaps a different car would have served you better. But hindsight is always 20/20 so that ship has sailed. And none of us know, maybe your circumstances have changed since then.

Having said that and speaking for myself and myself only, if the best fuel I could buy at the pump were imposing a burden on me now I’d sell the car in a flash and buy something that better fit my budget. The difference between octanes is the most insignificant money you’ll ever spend on the car. Believe me, the expenditures only get bigger from there.

 

[ZXMustang]

@AZ_Ryan I have modified my post to be more respectful, as I should be. IMO knock sensors for adaptive timing (even self retarding variable camshaft timing) that detect "ping" pre detonation etc. are often referred to as "oh shit" meters because by the time the detection and retardation are done so has some amount of damage. There is always a lag. They are meant for a serious one or two times problem not intended to constantly correct for low octane gas. Under that condition cumulative damage will occur. What mystifies me is that - unless I am totally wrong - most of the forum members are not one pay check away from a mortgage foreclosure.....so why would we discuss if we can use cheaper gas and oil when both are so critical to these, arguably, high performance engine's performance and longevity. It seems to me to be penny wise and dollar foolish. I have held, many times, pistons and seen cylinder sleeves subjected to pre-detonation, run on etc. They were from significantly damaged engines.

None of what you said is factual in any way.

Coming from someone who tunes these cars professionally, the stock tune "rides the knock sensors" just about every time you drive if you are running anything less than 91. If you run 87, you are getting KR on every spirited run. If you run 93 even at sea level, we see KR in stock cars getting tunes. In order to alleviate this, we dial in the maf to get fueling more accurate for the current DA, then we add some fuel for PE to give the car a fighting chance. Then we can inch in spark adders up to where the KR starts to "knock" on the door again. Then back off a degree and you're done. But KR isnt a problem for these cars. They run in microseconds pulling spark. The recovery from KR back to spark advance is slow, 6 seconds at times near redline. Those are values we drop dramatically so the car will get back to advance quicker after a short KR event.

 

[LouG]

Two things a previous post said. There is detonation and there is pre-ignition. There is no pre-detonation.
Pre-ignition is when the mixture is ignited by something before the spark plug fires. It could be carbon build up, badly machined combustion chamber, etc, etc. Pre ignition is easily detected by a metallic rattle under load at low rpm, it also causes run on. That's when an engine continues firing briefly after the ignition is off.
Detonation is when the mixture explodes rather than fully burns before the flame front ignites it. This instantly causes a spike in cylinder pressure and heat.
Neither are good, but high speed detonation is an engine killer.

 

[AZ_Ryan]

None of what you said is factual in any way.

Coming from someone who tunes these cars professionally, the stock tune "rides the knock sensors" just about every time you drive if you are running anything less than 91. If you run 87, you are getting KR on every spirited run. If you run 93 even at sea level, we see KR in stock cars getting tunes. In order to alleviate this, we dial in the maf to get fueling more accurate for the current DA, then we add some fuel for PE to give the car a fighting chance. Then we can inch in spark adders up to where the KR starts to "knock" on the door again. Then back off a degree and you're done. But KR isnt a problem for these cars. They run in microseconds pulling spark. The recovery from KR back to spark advance is slow, 6 seconds at times near redline. Those are values we drop dramatically so the car will get back to advance quicker after a short KR event.

Any idea what the HP differences would be with 87 or 89 octane?

 

[ZXMustang]

Any idea what the HP differences would be with 87 or 89 octane?

When you are seeing KR, its about 5-10 hp per degree pulled. And you might see 2-3 degrees come out at 91+ from time to time. With 87, could be more. So I bet on 87 in poor conditions, you would see -40 to -50 hp. Dont forget about cat over temp that runs you down to .70 lambda in full enrichment. That alone is going to soak you in fuel and kill a ton of HP.

Theoretically there is no difference if you are not seeing KR. But you will be seeing substantial KR on 87 at just about any load over .70 airload. Which is 3/4 throttle+. NA airload tops out around 1.05 airload.

 

[Bear376]

My old Mustangs are the econobox versions, but my 2025 is a GT because I wanted at least one last shot at the power. I run 91 in my 2013 and 2019, so I am not about to run anything less in my 2025. That is my call. Ford dials back the timing when the octane is lower than optimum, but it defeats the reason to pay the high premium price of a V8 performance engine. As long as the OP understands that his performance will suffer and he should not punch it as hard, it is his call.

 

[AZ_Ryan]

When you are seeing KR, its about 5-10 hp per degree pulled. And you might see 2-3 degrees come out at 91+ from time to time. With 87, could be more. So I bet on 87 in poor conditions, you would see -40 to -50 hp. Dont forget about cat over temp that runs you down to .70 lambda in full enrichment. That alone is going to soak you in fuel and kill a ton of HP.

Theoretically there is no difference if you are not seeing KR. But you will be seeing substantial KR on 87 at just about any load over .70 airload. Which is 3/4 throttle+. NA airload tops out around 1.05 airload.

Thanks for the education.

 

[MAT1955]

@ZMMustang.....so with the factory tune you "ride the knock sensors" if you don't use 91. Perfect - really good for the engine. What did I just say? Tuners who tune to then have to counteract their work to - your words - give the engines a "fighting chance". Their is lag in any tune either OEM or aftermarket. Any tunes are somewhat destructive. Tuners have to mitigate the destructive consequences of their actions. You made my case. KR is a problem for every car using too low an octane or poor tunes (many forum reports of lousy tunes and consequences) What you said makes perfect sense as it confirms, to me, all the negative aspects that I warn of. IMO most tuners are the scourge of the automotive world and damage far more vehicles than they help. Those that they do enhance performance on is usually short lived before damage shows. You have confirmed a lot of what I have said and I certainly stand by my comments. BTW we often discuss that tunes violate warranty even if done by a dealer. The dealer's promise does NOT speak for Ford (a different Corporate entity) if you want to risk a tune you had better open a case with an approval number from Ford Customer Service as what your dealer or joe the tuner say regarding OEM warranties means $hit all.

 

[robvas]

There were some people that dynoed the 24's when they first came out, full of 87 from the dyno

VMP added some Boostane to make "93" and gained like 20hp

 

[ZXMustang]

Nothing you said was confirmed. If a stock car was never tuned and drove for 100k miles on 87, the only issue it would have had was not making the advertised power consistently. No engine damage would have been done in most circumstances. Knock retard is not hurting the engine, it’s only hurting the power. The engines are perfectly safe mitigating knock with their knock sensors.

 

[Kevi]

There were some people that dynoed the 24's when they first came out, full of 87 from the dyno

VMP added some Boostane to make "93" and gained like 20hp

So hardly noticeable daily driving? What's that 2 tenths in a 1/4 mile or something?

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