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No gain unless the engine is tuned to use it. Well there is a gain to the oil companies profits, 😆.
 
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No, the stock tune on the PCM does not take advantage of the higher octane.
The results at least with the R/T (and the BMW --- I didn't bother to read the results of the Ford truck -- indicate there is some benefit to 93 over 91. But probably not worth the extra cost as the fuel mileage showed some slight improvement but not enough.

Does suggest though if one tracks the car a "full strength" load of 93 might be advisable unless the track offered no lead high octane race gas.
 

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Turbo motor. Ford detunes them, so that they can run 87, but will see improvements with 93.
Surprised that Ford does that. Well, maybe not so surprised. Selling a pickup that requires 91/93 would be a death sentence given how the majority of buyers feel about premium. I mean I didn't blink an eye when I bought my Porsche with its 93 recommended 91 just "barely" ok (I think the limit was 90). But a Ford F-150 buyer would probably scream bloody murder at seeing the truck "required" 93/91.

Recalled when I had a chance -- finally -- to run 93 in my Porsche 996 Turbo. The engine's performance was noticeably improved. Just 2 octane points above 91 and the engine really showed its appreciation. Remarkable transformation. Whie I knew how much benefit there can be to running with as advanced timing as possible -- Porsche documentation claims the engines are run right at the point of incipient detonation -- and 93 (vs 91) raises the point at which detonation occurs and thus this lets the engine controller run more timing. Still it was nice to have confirmation of this by actually running 93.
 

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I don't know - people spend way more for "upgrades" that provide even less HP/torque benefits... I mean their tests showed +14hp and +23 ft. lbs. of torque - just from using different gas. People pay a fortune for these expensive "cold air" intake and other upgrades which net no or very small power gains. Seems like a bargain to me! :)
 

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I don't know - people spend way more for "upgrades" that provide even less HP/torque benefits... I mean their tests showed +14hp and +23 ft. lbs. of torque - just from using different gas. People pay a fortune for these expensive "cold air" intake and other upgrades which net no or very small power gains. Seems like a bargain to me! :)
There is something to what you say. But human nature being what it is...

Higher octane gasoline -- provided of course the engine controller can take advantage of this -- even if one is not at the track can provide some benefit. With the ability to run with more timing the engine's low RPM tractability is improved. This results in a better "drive" as in most cases when we drive our cars it is not at WOT but at part throttle around town or on the highway.

(As an aside my Boxster with its 11.3:1 compression ratio even with 91 -- which is all I could get in CA -- its around town manners were impressive. That was one very tractable engine even with just 2.7l of displacement. High compression and with the proper grade of gasoline is the reason.)

But even on the highway the engine controller can dial in more advance which among other benefits improves gas mileage.
 

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I'll admit it - I've used 93 octane fuel in all of my cars for as long as I can remember. I just prefer to use the fuel that will give my engine the best chance to run as well as it car - regardless of the car.

I got into tuning with HPTuners with my other car (2012 Impala) and was amazed at how much knock retard there was at certain places - even with 93 octane gas! With 87 it was way worse. At least with the GM ECM controllers, it starts with a "high octane" table for timing and then reduces the timing towards the "low octane" table if/when it sees knock. So you start off with the most timing and it lowers it from there. It's not like most people think where it starts low and goes up if there is no knock - it's just the opposite.

For me and how much I drive, I don't feel the extra cost is a big deal. If it helps make my engine a little happier and ends up knocking a little less, that's a good thing. It can only help.
 

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The results at least with the R/T (and the BMW --- I didn't bother to read the results of the Ford truck -- indicate there is some benefit to 93 over 91. But probably not worth the extra cost as the fuel mileage showed some slight improvement but not enough.

Does suggest though if one tracks the car a "full strength" load of 93 might be advisable unless the track offered no lead high octane race gas.
your 5.7l is not even tuned for 91 octane.
 

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I'll admit it - I've used 93 octane fuel in all of my cars for as long as I can remember. I just prefer to use the fuel that will give my engine the best chance to run as well as it car - regardless of the car.

I got into tuning with HPTuners with my other car (2012 Impala) and was amazed at how much knock retard there was at certain places - even with 93 octane gas! With 87 it was way worse. At least with the GM ECM controllers, it starts with a "high octane" table for timing and then reduces the timing towards the "low octane" table if/when it sees knock. So you start off with the most timing and it lowers it from there. It's not like most people think where it starts low and goes up if there is no knock - it's just the opposite.

For me and how much I drive, I don't feel the extra cost is a big deal. If it helps make my engine a little happier and ends up knocking a little less, that's a good thing. It can only help.
For the cars I owned that the factory called for 93 I would have run 93 had it been available. But in CA 91 is all there is.

With other cars I have run what the factory calls for. 87 for some engines, 91 for others. In the case of one engine that the factory called for using 87 I tried 91 but there was no apparent benefit. The engine still pinged upon take off from a stop -- it pinged the entire 150K miles I put on the engine -- and under other operation conditions manifested no benefit I could detect.

Of course the engine for which the factory recommended 93 did react favorably when I had a chance to use 93.

With my Hellcat I have not found 93 here. I have found 91 ethanol free. As best I can tell the Hellcat engine does not react favorably or unfavorably to this. But i like to run it in both my vehicles as it is carried by a conveniently located gas station and the price is very attractive. The other day I filled the Hellcat with some of this gasolne and paid just $2.07/gallon. (This down from $2.14/gallon just a week or two prior.)

By my observation the timing retard under certain conditions can be high. But it is "normal". For example with my 2006 GTO I would observe the timing. In 6th gear -- manual transmission -- with the engine RPMs above 1K but not by much -- timing was quite advanced, in the 35 to 36 degree range. As an aside the instantaneous fuel mileage number was very high -- over 30mpg -- at the same time. But just a tiny press on the gas pedal would cause the timing advance to fall to 25 or even a bit lower. And that 30mpg went bye bye to around 15mpg or even lower.

The engine controller is reacting to the engine knock sensors along with (probably) some "input" from the engine fuel/timing maps.

Under hard acceleration the timing advance would drop. This is more due to the engine fuel/timing maps I suspect as under hard acceleration the engine controller can provide a richer mixture. A richer mixture does not need as much advance.

Bottom line is ignition timing is a very dynamic data item. The engine controller with the input from the knock sensor, the fuel/timing maps, engine temperature, and other things is constantly adjusting the timing.
 

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your 5.7l is not even tuned for 91 octane.
I do not own a car with a 5.7l engine. (My Hellcat of course has the 6.2l engine and I always run 91.)

I was just noting that the fuel test apparently found the test car with a 5.7l engine appeared to run better with a higher octane grade of gasoline. Which surprised me as I would not have expected the engine controller to have the capability to take advantage of a higher grade of octane.
 

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I could definitely see how it would. Anything to stop the knock sensors and computer from pulling timing so your engine is running to more of it's full potential under hard driving conditions would be seen as a healthy "gain" in power.
 

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I could definitely see how it would. Anything to stop the knock sensors and computer from pulling timing so your engine is running to more of it's full potential under hard driving conditions would be seen as a healthy "gain" in power.
My experience is with cars circa 2006 (my GTO). Except for my Porsche cars (2002, 2003, the 2008 was only around for 4 weeks...) my other cars fueling them with a gasoline with a higher octane rating than the car maker called for was a waste.

As best I could tell there was no change in engine performance. If the higher octane allowed for less timing retard I could detect no signs of this.

But maybe things have changed since 2006 and (in this context) Dodge has given the engine controller the ability to taken advantage of more octane that the engine nominally calls for.

(I have not yet had the opportunity to run 93 in my Hellcat to see if the engine likes 93....)

Or another way of looking at it is the egnine timing is a bit aggressive but often dialed back when the owner uses the recommended octane of gasoline. The timing is run advanced so the engine runs right at the borderline of detonation. But with higher octane gasoline the timing can be more advanced even more instead of dialed back as much or at least as often.

Thus it would appear that contrary to the usual thinking that running a higher octane of gasoline is of no benefit it might be worth the trouble to try some just to see if there is any noticeable change and for the better. If there is then one would of course have to decide if the benefit is worth the extra cost of the higher octane gasoline. In some cases better mileage arising from the use of a higher octane of gasoline might offset its extra cost.
 

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I do not own a car with a 5.7l engine. (My Hellcat of course has the 6.2l engine and I always run 91.)

I was just noting that the fuel test apparently found the test car with a 5.7l engine appeared to run better with a higher octane grade of gasoline. Which surprised me as I would not have expected the engine controller to have the capability to take advantage of a higher grade of octane.
its allowing the engine to run more timing advance (within its stock tuning) - its a function of the knock sensors not detecting spark knock and pulling timing.

the 1/4 mi times pointed out the upper end power and the slight increase in MPG.

The tuning is conservative to factor in the gasoline grades vary by state / elevation and oxygenate formulation (CA and high altitude)

some of the high desert areas premium maxes out at 90 octane and CA has 91 octane max

In theory the tuning could be optimized (93 octane in my area), but if I were traveling outside the area, the grades of fuel might not be as high
 
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Discussion Starter · #17 ·
No, the stock tune on the PCM does not take advantage of the higher octane.
I take it you didn't read it. No tune change and there was a 14HP and 23tq gain.
 

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some have a mistaken idea of what octane readings mean. A lower octane like 87 burns hotter and faster and is a more powerful fuel then 93. What octane is is a burn retartant that advantage is you can tune your car (more timing advance) which in reality is static compression which will increase power. No timing added not power increase. As a matter of fact a decrease. What a 93 octane tune does is advance timing and in some case lean our your fuel air mixture. Do that with regular and your motor will detonate. Burn the octane rating the car manufacture recomends or the octane rating your programer is set for or the tuner put in it. That is the ideal fuel for power and gas mileage. Adding more octane if anything makes it worse. I remember years ago when we were racing snowmobiles. We used race gas in them because they had porting and head work done and that increased compression. Sponsor bought all the race gas we wanted so we ran it in our trail sleds too until we found out when it got below zero they wouldnt even start. Couldnt get that high octane fuel to even light.
 

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Discussion Starter · #19 ·
some have a mistaken idea of what octane readings mean. A lower octane like 87 burns hotter and faster and is a more powerful fuel then 93. What octane is is a burn retartant that advantage is you can tune your car (more timing advance) which in reality is static compression which will increase power. No timing added not power increase. As a matter of fact a decrease. What a 93 octane tune does is advance timing and in some case lean our your fuel air mixture. Do that with regular and your motor will detonate. Burn the octane rating the car manufacture recomends or the octane rating your programer is set for or the tuner put in it. That is the ideal fuel for power and gas mileage. Adding more octane if anything makes it worse. I remember years ago when we were racing snowmobiles. We used race gas in them because they had porting and head work done and that increased compression. Sponsor bought all the race gas we wanted so we ran it in our trail sleds too until we found out when it got below zero they wouldnt even start. Couldnt get that high octane fuel to even light.
Good point on the rate of burn, if you compare gasoline to diesel fuel i.e.. Octane vs. Cetane ratings. The higher the cetane rating the faster the burn octane creates more of a controlled even burn where Cetane creates for lack of a better term more explosive burn.

If anyone wants to geek out on it here's an Engineering Explained:
 

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I always said the higher the octane, the higher the flash point of the fuel, so in a high compression engine or one with higher cylinder temps due to advanced timing the more resistance to preignition.
 
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