What grade fuel do you run?

[DT444T]

41,000 miles on 3.5L 2021 non-hybrid, 87 octane (up to E10 in my county) on every fill because the manual says it's fine. Have poured in a bottle of Seafoam every 8 months or so just because. No issues. Mild towing (~1000 miles with 2200 pound trailer).

Similar, except yes-hybrid and have towed more often and heavier (not a d-measuring contest).

I have always ran 87. When I get my travel trailer I will probably try 91+ fuel to see if it gets better mpg while towing.

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[JExpedition07]

Did 93 octane this tank, it might be placebo but it feels like she pulls harder on the low end when filled with premium

 

[Chili]

87 octane in my 3.5. If I tow something big I'd use 89. It doesn't have ping issues like my 2020 5.0 did on 87.

 

[Graygoose2021]

Did 93 octane this tank, it might be placebo but it feels like she pulls harder on the low end when filled with premium

Mine too, more timing, more power

 

[EricR]

87 day to day.
91 when towing.

It would be interesting to try 93, but I haven't seen it in the Boise area, or while traveling with the trailer.

 

[JExpedition07]

I have seen an increase in MPG with the 93 octane as well. Im averaging 18 combined (what the EPA sticker says). This is the first truck I’ve ever had that actually gets what the sticker said it would lol. I was getting 17 with the 87. This however could also be attributed to the fact it’s breaking in. I have 650 miles so far. Either way the 5.0 seems happier on the 93 octane. It idles very quietly and shifts like butter.

Not that it ran bad on 87, I can just feel it has extra power and a quiet idle on premium.

 

[bmanxx13]

I fill up with 91 every time in my ‘22 5.0. When I had a 3.5L eco boost I also filled that up with 91.

 

[XLT22]

For you guys at altitude it's REALLY important to remember to not use a fuel with less than 87 octane on the Ecoboost engines. The turbochargers compensate for the altitude difference.

 

[Rockman5159]

Perfect, I learned something new

I have a 2021 FX$ with the 5.0 ans I use 93 ethanol free and if thats not available I use 91 octane.just runs better to me

 

[doolin64]

89 with my Powerboost, all the time.

 

[STMF420]

A few things to perhaps note ....

• The PCM system on these engines is very sophisticated
• Your 5.0's PCM has the ability to vary intake and exhaust cam timing independently (Ti-VCT), as well as injection timing / duration, spark timing / duration, etc
• PCM manipulation of valve timing and overlap can reduce the actual effective compression ratio below the stated possible maximum, on-the-fly (that stated 12.x:1 isn't fixed in stone)
• The 3.5EB has even more variables PCM can tweak on-the-fly to manage what's happening in the combustion chamber (boost-related variables)
• In both cases there's sophisticated sensors ('knock sensors' among many others) to provide PCM feedback, allowing it to adjust those variables and preclude potentially damaging combustion conditions.

As long as you stick with fuels in the recommended spec range, all of those things protect your engine and, I would suggest, don't 'ask a lot' of a given fuel but do 'take advantage of everything' a given fuel can deliver when that is demanded by driving conditions .

Yeah, that means that a lower-octane fuel may not (won't) deliver the same performance as a higher octane fuel, particularly under stressful loads, but at least you're protected from engine damage if you try to over-reach a given fuel's capabilities.

All just for your consideration.

Me, I burn 87 octane in my 3.5EB for my daily un-stressed driving; I fill with higher octane before a more stressful adventure towing my RV; I don't see benefit in running a more expensive higher-octane fuel with power-delivery capabilities that won't be used in my sedate daily driving. Your driving conditions and habits may vary and warrant a different approach, No Worries!

Yeah, no matter the octane I stick with fuels having good additive packages (e.g. Top Tier) in the interest of long-term engine health

If the engine adjusts to how it is running mostly because of load + octane does it have a memory. I mean if it learns how to throttle at different loads because of octane ,then when you change the octane does that mean it has to learn again. If so seems it would be best to stay at one octane as much as possible.

 

[Buyer2021]

If the engine adjusts to how it is running mostly because of load + octane does it have a memory. I mean if it learns how to throttle at different loads because of octane ,then when you change the octane does that mean it has to learn again. If so seems it would be best to stay at one octane as much as possible.

This characteristic does not have a "memory" in the sense of the "Learned Adaptive Transmission Strategy" (for example).

The PCM is constantly adjusting on-the-fly (it continuously 'polls' the pertinent sensors very rapidly, many times per minute / second) in order to ensure the engine is protected from damage / running optimally based to rapidly changing load / octane / driving conditions.

So, just as when you drive on level ground for hours or days and suddenly but safely enter a steep grade (suddenly increase the engine load), you can drive with octane "X" for days or months and then suddenly but safely alter what's in your tank by introducing a different octane; in both cases the PCM will respond to those changed conditions 'instantly' (as soon as the 'new / different octane' enters the combustion chambers).

As the name suggests, the transmission memory can be thought of as relating to "stragetic" (mid / long term) operation; the PCM response to load and octane can be thought of as relating to "tactical" (short-term / immediate) operation.

 

[Wookie]

Ethanol free premium

 

[cb4017]

So far 91 octane, which is the best I can get around here.

 

[diambo4life]

First tank on 93 since the SC went on. Was running 91 and E85 before that. Nothing less....because my baby has to drink the good stuff.... lol.

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