Going from 87 to 93 octane

[dnand]

This feels like a dumb question. I've read posts suggesting how to transition from 87 to 93. From what I gathered, get as close to empty with 87 as possible then put in 93. But I also read something about tune. Confused what tuning entails? I do have Forscan that I can use but no tuner. Would love any guidance with this.

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[JExpedition07]

No tune required, add whenever you want and the truck will adjust over the next tank or two

 

[Eskram]

You don't need to do anything special really. It's not a bad idea to run the tank of 87 near empty so you're getting more 'pure' 93 than a mix of 87/93. The computer will adjust the timing a bit as it 'sees' the higher octane fuel.

Tuning is essentially editing the ECU/Transmission tables to gain more power and smoothness. There isn't a DIY method I'm aware of - you'd pay for a device that will allow new mapping to be flashed to the truck. Livernois and 5 Star are two companies that can provide a tune. Where the confusion about 93 octane may lie, is that many of the performance tunes require 93 in order to make the stated power safely.

 

[TexasTruck]

That's about it.... try not to mix 50/50, but it sounds like you didn't. As far as the "tuning" the engine will automatically adjust to the new fuel.

 

[dnand]

Thank you all so much! I was going crazy trying to figure out what else I had to do but looks like I did what needed to be done.

 

[Gros Ventre]

The octane rating will come out proportional to the ratios of each in the mix. The closer to empty when you refill the higher the octane of the mix. If you're a purist, do several tanks down to near empty and fill with 93...

 

[Tremoring4fun]

Now let me ask a dumber question, can you really feel a noticeable gain just from 87 octane to 93 without a tune?

 

[JExpedition07]

Now let me ask a dumber question, can you really feel a noticeable gain just from 87 octane to 93 without a tune?

Definitely can on the 5.0L V8 under WOT, purple is untuned on 87 and blue is untuned on 93. Red is only tuned line. Peak power stock on 87 is 348 wheel horsepower @6,000 and peak power on 93 is 370 wheel horsepower @6,000. That’s 22 horsepower difference, not huge but it exists. You really feel gains above 4,000 rpm…..so if you are running times then yes it’s worth it, otherwise not for just tooling around.

 

[Tremoring4fun]

Great info, thanks for sharing

 

[JExpedition07]

Great info, thanks for sharing

Ford rates the engines per the SAE standards on 91 octane. They make more power using an octane beyond 91, and less power using an octane rating under.

If you extrapolated those #’s shown to the crankshaft with a typical 12% drivetrain loss factor that 5.0 was making about 393 horsepower on 87, and 415 horsepower on the 93 octane. Ford is pretty conservative on the ratings, the 3.5 EcoBoost and 5.0 both put down well over 400 HP on 93 and ethanol mixes

 

[Aron]

That's about it.... try not to mix 50/50, but it sounds like you didn't. As far as the "tuning" the engine will automatically adjust to the new fuel.

Wouldn't that just get you ~91 octane (e.g., "mid-grade") gas for that tank? Why would that be bad?

 

[MJG44]

^^Not bad...just spending the $ for 93 while getting a mixed octane on that tank. I suppose it is proportionate to spending half fill of the tank at the 93 price point.

I have a flex tune from Livernois...there is 94 available to me here and always fill up with that but in the odd circumstance out of town, I have to use 91. I let the tank run empty on 91 before refueling with 94.

Couldn't tell you the stock tune difference from 87 to 93 because I didn't try that on my 5.0.
I can tell you my stock tune '22 high output ecoboost Expedition, there's a noticeable difference between 87 and 91.

 

[TexasTruck]

Why would that be bad?

I don’t think it’s bad, but I was advised by a “tuner” company that I used. In general, the programming will flex based on the fuel type. Something about the proportions and computations to map it properly. Eventually you have 100% 93, so rather than 2 or 3 fill ups to achieve 100% and the computer adjusting each time, do it once… more or less…

 

[Jimi]

You don't need to do anything special really. It's not a bad idea to run the tank of 87 near empty so you're getting more 'pure' 93 than a mix of 87/93. The computer will adjust the timing a bit as it 'sees' the higher octane fuel.

Tuning is essentially editing the ECU/Transmission tables to gain more power and smoothness. There isn't a DIY method I'm aware of - you'd pay for a device that will allow new mapping to be flashed to the truck. Livernois and 5 Star are two companies that can provide a tune. Where the confusion about 93 octane may lie, is that many of the performance tunes require 93 in order to make the stated power safely.

Does the PB get the same noticeable difference? ?

 

[Eskram]

Does the PB get the same noticeable difference? ?

Yes, but my truck has only had once, what I assume was 87 - the dealer fill up. I've always run 93 in my vehicles, partially because all have been tuned, and FL is hot and I'll take any extra insurance I can to not grenade a motor to save a few bucks.

With a tune, an astounding 'FUCK YEAH!'. It's a completely different truck.

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