Gas Octane

[BaileytheDog]

Here in my area of Wisconsin, I can get 91 without ethanol, or 93 with ethanol.
Stock 2023 GT (5.0).
Is there a preference for either? I'm not taking it on the track, so if it is a HP difference, I doubt I would notice.
Thanks

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[shogun32]

91 without.

 

[engineermike]

If you don’t care about power, 91 without. But 93 e10 is “free” hp.

 

[shogun32]

If you don’t care about power, 91 without. But 93 e10 is “free” hp.

why would you put an engine 'carcinogen' into your car if you can avoid it with basically no penalthy?

 

[SheepDog]

93 with. The 10% ethanol and higher octane will allow the PCM to add a bit of timing over the 91.

 

[engineermike]

why would you put an engine 'carcinogen' into your car if you can avoid it with basically no penalthy?

The gen3 coyote is knock limited stock even on 93. You’re giving up 2 octane numbers, not to mention the ethanol has some additional knock advantage over and above what shows up in the octane number. I bet it can run 2-4 more deg timing on the 93 e10.

I run (and pay through the nose for) e0 91 in my boat, atv’s, and mower because they all have atmospheric vented fuel systems, so any ethanol in fuel would absorb moisture from the air and cause real problems. But the mustang’s fuel system is sealed and all the materials are compatible with ethanol so I’m not worried about the downsides.

 

[shogun32]

93 with. The 10% ethanol and higher octane will allow the PCM to add a bit of timing over the 91.

...

I bet it can run 2-4 more deg timing on the 93 e10.

which is relevant what, over 5500 RPM and full-tilt throttle?

 

[K4fxd]

You will get 10 to 30% better gas mileage with E0 gas. Too bad they don't offer E0 93.

 

[engineermike]

...

which is relevant what, over 5500 RPM and full-tilt throttle?

Full throttle and probably 4000-4500 and up.

 

[SheepDog]

You will get 10 to 30% better gas mileage with E0 gas. Too bad they don't offer E0 93.

Maybe 10%. 30% is the difference between E85 and pump gas

 

[GregO]

Here in my area of Wisconsin, I can get 91 without ethanol

Kwik Trip fuel station ?
Off Road 91 pump for powersports/small engines ?
If yes I’d take into consideration the age of the fuel sitting in the storage tank.

 

[Pistol_91]

Which ever one is cheaper brother

 

[BaileytheDog]

Kwik Trip is 93 @ 10% and the county my work is in has no ethanol 91 at a few stations.

Kwik Trip fuel station ?
Off Road 91 pump for powersports/small engines ?
If yes I’d take into consideration the age of the fuel sitting in the storage tank.

 

[K4fxd]

Maybe 10%. 30% is the difference between E85 and pump gas

I used to have a station that sold E0 93 close to me. I got 3 to 5 mpg better mileage vs E10. 5 MPG better on the freeway. E0 is all around better fuel.

 

[SheepDog]

I guess it just depends on what the objective is. I'd be curious to see some logs with each fuel.

We only get E65-E75 Ethanol here, and I haven't seen any indication of corrosion or gummed up filter, injectors etc. Maybe E70ish is the sweet spot to have enough gasoline in the mix to keep things clean. My 2017 ran on nothing but "E85" for 4 years. Never once had a tank of gasoline in it. I think the consistent low humidity here also plays a part in this though.

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