89 Octane and hot weather.

[Osco]

I read somewhere that in really hot weather higher octane can make a performance difference under certain conditions.
I’ve been on 89 for two tanks now and can feel a difference.
Mpg’s are no different, still averaging 25.5 mpg in my Appalachian mountains.
I am NOT granny driving nor am I lead footing it.
I know so many do and then post higher mileage averages.
Flat landers pfft.
I also know the dash computer figures are skewed to show us higher mpg’s.
My posted average is figured the old fashion way, the far more accurate way.
I feel no real power gains but my 1.5L feels just a little smoother and a little more responsive on take off and during low gear acceleration.
Just enough to notice.
Last month in the same heat I did premium 93 octane for two tanks. It felt just like I described the 89 mid grade fuel.
In all my past 4 cylinder engines I never noticed any difference in mpg’s or felt power but this is my first turbo equipped motor.
It’s subliminal but enough that I will continue on 89 oct for July and august.
Things start cooling off here in September.
I am paying $4.59 for 87
and $4.89 for 89 octane.
Premium here is $5.39.
I drive 150-200 miles a week at most with some weeks less than 150 so the extra cost is minimal.
,
Just an observation that surprised me.

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[Fossil]

high engine temps can cause pre ignition (ping) and higher octane fights that.
the ECU real time monitors ping and usually retards timing (among other things like reducing boost) which can affect mpg and performance.
haven't really heard about BS having any overheat issues though.

 

[13MikeH]

I read somewhere that in really hot weather higher octane can make a performance difference under certain conditions.
I’ve been on 89 for two tanks now and can feel a difference.
Mpg’s are no different, still averaging 25.5 mpg in my Appalachian mountains.
I am NOT granny driving nor am I lead footing it.
I know so many do and then post higher mileage averages.
Flat landers pfft.
I also know the dash computer figures are skewed to show us higher mpg’s.

Ironically just read an article, it was noted the Ford due to empty and mpg calculator onboard are considered the standard all other manufacturers should follow. It was rated the best in industry for consistent accuracy. One of the tests, at Michigan Speedway they line up 200 plus vehicles and have drivers perform innumerable stress and calculation tests for days on end. It's a fleet of drivers pacing lap after lap. It was noted Ford has what is considered real world data on fuel consumption and dte values...so

 

[Mark S.]

high engine temps can cause pre ignition (ping) and higher octane fights that.

Ping or knock—more accurately called detonation—and pre-ignition are not the same thing. This video explains the difference.



Ford's engine management scheme requires at least SOME detonation to get the most power out of the engine. Unless you are using lower-than-recommended octane fuel the powertrain control module will dial back power output to prevent heavy or prolonged detonation.

 

[thekingprawn]

Is the theory that the higher temperature air is lower density?

 

[13MikeH]

Is the theory that the higher temperature air is lower density?

Yes. Cold air the race cars eat...dense air changes combustion

 

[Osco]

Ok July is over, been on 89 octane for several weeks.
It’s a slightly smoother running engine.
I must add that I think I feel a little faster spin up mid Turbo.

 

[Mark S.]

Is the theory that the higher temperature air is lower density?

It's not really a theory, it's a provable fact:

https://www.grc.nasa.gov/www/k-12/Summer_Training/FranktonES/Convection_main_page.html

 

[Osco]

Thanks Teacher, that was great !
It seems these days the obvious, the simplest science is dismissed.

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