Engine On stock GT - any benefits to higher octane gas?

MrPerfect2 · Jul 26, 2019

No mods on car 91 . I tried several gasoline brands and several octane ratings . Is there any positive or negative effects of brands and octane ratings ? Is the 87 octane better for full detonation on a non modded 5.0 ? Does it burn hotter and will it increase engine temps ? Will the stock Computer under WOT automatically advance the timing to a higher degree if higher octane is used ? I know most everyone has mods done and for them it may be different , but my car is just a clean stock daily driver . Thanks

DSB88GT · Jul 26, 2019

You would be wasting your money using anything other than 87.

MrPerfect2 · Jul 26, 2019

Ok - aside from $ aspect - what happens when you use 87 vs 93 , anything ? Does anything change - runs hotter ; more or less power ? More complete combustion ?

Mustang5L5 · Jul 26, 2019

Do you have detonation with 87 octane? If not...keep running it.

Mustang5L5 · Jul 26, 2019

MrPerfect2 said:
More complete combustion ?

Actually, less.

Lower octane burns quicker and more complete. Higher octane just resists burn, so it helps combat pre ignition when used in power adder, or modified applications.

Ideally, you want to run the lowest octane you can get away with without detonation (pre ignition). If you are bone stock (timing set to 10 degrees), stick to 87 unless you have detonation. Detonation in older cars can be caused by carbon deposits on the heads if the engine is rather dirty. So in some cases you may need to run 89 octane or so to avoid this.

MrPerfect2 · Jul 26, 2019

Ok - it runs great on 87 - no pre-detonation sounds from idle to WOT - I will stick with 87 - thanks

Real time recon · Jul 26, 2019

Only burning 93 no ethanol gas here.And getting a nice blue flame LOL

JD1964 · Jul 26, 2019

What if you set your ignition timing more advanced on a stock setup. When mine was stock I bumped the timing to 14 and felt a noticeable improvement in performance. 93 octane can help fend off spark knock of more advance timing cant it?

Mustang5L5 · Jul 26, 2019

Then you would need higher octane to resist burning your fuel prematurely due to timing advance

JD1964 · Jul 26, 2019

So correct me if im wrong. The stock 10 BTDC setting is aimed at reduced emissions? Hence, at 10 you sacrifice some performance for cleaner exhaust?

Mustang5L5 · Jul 26, 2019

10 degrees base timing is where Ford set it from the factory and based its ECU programming on. You get lower emissions and reduced chance of detonation in most driving conditions. In other words it's safe for most average driving conditions and won't damage the motor

Bump the timing and power goes up, but also some negative side effects such as increased emissions and detonation...hence the need for higher octane.

Scope of this thread is really towards stock cars.

FastDriver · Jul 27, 2019

Preignition: Ignition before spark

Detonation: End gas 'detonation' after the spark

Preignition is typically caused by a heat source in the cylinder, like the ground strap on a plug with too high of a heat range. Detonation is caused when the flame front causes pressure/temperature in the unburned end-gasses to rise over the auto-ignition temperature of the fuel. Higher octane = higher auto-ignition temperature in a given fuel type. Hence, higher octane resists detonation, but this can also be accomplished by cooling the A/F mixture before the spark or by running a richer mixture that resists detonation through evaporative cooling, which ultimately keeps the end gas temps down below auto-ignition temp.

Preignition is deadly and instantaneous. The fuel typically burns completely as the piston is still rising to compress it. Detonation can be deadly, but mild detonation typically is not, at least initially. Detonation unchecked can lead to preignition as pieces of piston, plug, ring, head or other material is picked off and remains as a "hot spot" in the cylinder that potentially ignites the incoming mixture. Obviously, unless you are tuning on the ragged edge in an engine-masters shoot-out, you don't want detonation, either.

Answer to title question for a good condition stock engine, including timing as Mike stated, is no.

MrPerfect2 · Jul 27, 2019

Thanks guys ! Excellent feedback , hope others ( and me ) learned from your explanations!

Engine On stock GT - any benefits to higher octane gas?

MrPerfect2

DSB88GT

Active Member

MrPerfect2

Mustang5L5

That is…until I whipped out my Bissell

Mustang5L5

That is…until I whipped out my Bissell

MrPerfect2

Real time recon

Mustang Master

JD1964

there is enough sticking out to grab on to

Mustang5L5

That is…until I whipped out my Bissell

JD1964

there is enough sticking out to grab on to

Mustang5L5

That is…until I whipped out my Bissell

FastDriver

I was uncomfortably high & wearing a helmet

MrPerfect2

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Engine On stock GT - any benefits to higher octane gas?

Active Member

That is…until I whipped out my Bissell

That is…until I whipped out my Bissell

Mustang Master

there is enough sticking out to grab on to

That is…until I whipped out my Bissell

there is enough sticking out to grab on to

That is…until I whipped out my Bissell

I was uncomfortably high & wearing a helmet

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