What octane do you use

[Hack]

On fuel economy, I'd have to find out from people I know in calibration, but I can only think that the increase in octane allows for a small spark advance, so acceleration while cruising (6th gear, 2000 rpm) is more efficient. It's small (~3%), but I had about 20 trips back and forth between Chicago and Detroit last year to collect data on it.

It would be interesting to see an actual measured figure. I think around here they use greater ethanol content to increase octane. Since ethanol has about 30% less energy by volume than gasoline I would expect a measurable decrease in fuel economy.

I agree differences would be more noticeable at low rpm out of the main power band.

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[Quackfoo]

I'm sorry I don't understand why this needs 10 pages of debate? Ford says the car will run fine on 87, but run better on 93. If you don't mind the hp loss, run whatever you want. On the GT it's still like 410hp, which is still quite a bit of power. The Ecoboost guys have the tougher choice because it's more pronounced for their cars.

I'm sure there are plenty of people who run 87 who have plenty of money and hey that's their choice. But if you're really that worried about the $5 difference when you buy gas, you bought the wrong car. You let your ego buy a car instead of your finances and you should probably have bought a Civic. I'm sure that'll hurt someone's feelings, my recommendation is get over it.

 

[Hashbrownn]

Have you calculated dollar per mile instead of dollar per tank?

Yes, I have.
Most of my driving is done in the city, around 25-45MPH.
I am getting about 13MPG around town on 87.
I now get about 14MPG around town on 93.
that's is about 7% increase on MPG for 30%+ increase in fuel cost.
DOES NOT COMPUTE!! DOES NOT COMPUTE!!
I just cannot justify the increased fuel cost of 93, if you're just looking at the MPG.
93 does seem to have that extra kick on WOT, must be the additional torque.

 

[BmacIL]

It would be interesting to see an actual measured figure. I think around here they use greater ethanol content to increase octane. Since ethanol has about 30% less energy by volume than gasoline I would expect a measurable decrease in fuel economy.

I agree differences would be more noticeable at low rpm out of the main power band.

You're assuming that the octane rating increase is due to increased ethanol content alone, which at least where I drive, isnt accurate (all 10%). The difference is 93 is a decreased volatility blend of gasoline.

 

[jon2002]

You're assuming that the octane rating increase is due to increased ethanol content alone, which at least where I drive, isnt accurate (all 10%). The difference is 93 is a decreased volatility blend of gasoline.

How quickly does the ECU accomidate and adjust for more aggressive timing after switching from 87 to 93 octane?

Is it immediate? I've had cars in the past which required a coupe hundred miles of knock free operation before the ecu would get more aggressive.

Thank you

 

[redline727]

How quickly does the ECU accomidate and adjust for more aggressive timing after switching from 87 to 93 octane?

Is it immediate? I've had cars in the past which required a coupe hundred miles of knock free operation before the ecu would get more aggressive.

Thank you

When I had my knock/timing issue due to some crappy winter fuel, it was restored immediately after I used some Lucas Octane Booster. But I am tuned so I dont know if that makes a difference or not.

 

[ilkhan]

87 octane, because 425hp is still "enough" and 13mpg.

 

[BmacIL]

How quickly does the ECU accomidate and adjust for more aggressive timing after switching from 87 to 93 octane?

Is it immediate? I've had cars in the past which required a coupe hundred miles of knock free operation before the ecu would get more aggressive.

Thank you

Within a few miles/minutes it would begin adjusting.

 

[AZ_Ryan]

I gotta say some of these horse power claims seem pretty hard to believe.

I don't know jack about the ecoboost, but I cant imagine higher octane lets the computer advance the timing enough on the GT to get you 20-40 horsepower like some are claiming. Id like to see actual dyno runs that show this.

Also isn't it a well known myth that higher octane doesn't get you better gas mileage on a car that's engineered for 87?

 

[daltron]

87 octane, because 425hp is still "enough"

 

[FordTechOne]

Fixed.

You obviously don't understand what detonation is or how the PCM detects and adjusts for it.

I stated the following:

Detonation occurs when you run low octane/poor quality fuel in a high performance engine.


That is true on all engines, electronics don't prevent detonation. Instead, they detect detonation AFTER it has occurred, and then adjust parameters such as boost and timing in order to reduce/eliminate the detonation. The PCM cannot "see" the octane and adjust for it before detonation occurs :doh:

Therefore, when you run crap fuel (87/89 octane) in a high performance engine, you always run the risk of causing engine damage in the time it takes for the PCM to detect the detonation condition and adjust parameters for it. The chances of engine damage are obviously slim, but it's certainly not something I would take a chance with on a brand new high performance engine.

It simply amazes me that so many people on here that spent extra money to buy a high performance car continue to ask if they can run low octane fuel.

 

[FordTechOne]

I gotta say some of these horse power claims seem pretty hard to believe.

I don't know jack about the ecoboost, but I cant imagine higher octane lets the computer advance the timing enough on the GT to get you 20-40 horsepower like some are claiming. Id like to see actual dyno runs that show this.

Also isn't it a well known myth that higher octane doesn't get you better gas mileage on a car that's engineered for 87?

The only "well known myth" on here appears to be that engines like the 5.0 and Ecoboost were designed to run on 87 octane.

High performance engines like the 5.0 and Ecoboost are designed to run on 93 octane, period. That is why they can only produce their advertised horsepower and torque ratings on 93 octane fuel. Engineering creates a strategy that de-tunes the engine from it's optimal parameters when some cheap ass puts crappy fuel in it. That strategy retards timing and/or reduces boost in order to attempt to prevent engine damage from detonation.

On the 5.0, for example, the engine will continue to pull timing each time it detects additional detonation. Depending on engine load, RPM, engine temperature, and the quality of the fuel, that could easily mean 20HP to 40HP.

If an engine is designed and engineered for 87 octane, it is correct that running higher octane fuel should not affect engine performance or fuel economy.

 

[AZ_Ryan]

87 and 89 octane is now crap fuel? Higher octane fuel has nothing to do with fuel quality. All higher octane does differently is burn at higher temperatures and presure to resist detonation.

As others have pointed out, this engine IS designed to run on 87 octane. It's not going to hurt your car to run it otherwise the frigging manuals wouldn't say to run premium. It's not a conspiracy or a myth and you don't know better than the ford engineers who designed the engine.

If you want to believe other wise that's fine. But lets not spread your opinion as fact here.

As for the topic - I have no doubt the coyote engine produces optimal performance on premium fuel, but I call BS on a 20-40 increase in HP.

 

[AngelDeath]

Well I cant tell you I dont know much about all the details, but a few things I wanted to mention:

To the person who said manuals have to say 87 octane for marketability is wrong. I own 3 vettes, my 2001 AND my 2012 clearly state in the manual 93 octane, it states that 87 can be used but will take a performance hit, and the possibility of knocking, and is not recommended. Vettes are also high performance cars, yet it does not state you can use 87 octane.

Also ethanol additive doesnt increase fuel efficiency, but reduces it (Its "enviromental friendly" to reduce emissions), also unless things have changed in the last 10 years (Which I seriously doubt) 87 is as they say dirtier then 89 (which is only slightly better) or 93 (which has the least impurities). There is more impurities in 87 which cause deposits in the engine itself which after time causes build-up which also reduces horsepower, efficiency, and reduces the life of the engine.

My mechanic told me years ago to stay away from 87, he also said if you have a normal beater use 89 if you dont want to use 93. if you have ever looked at 87 octane gas it has a slight yellow tinge to it opposed to 93. And considering how cheap gas is right now, why is anyone willing to take the chance and nickel and dime on fuel when you just spend 1/4th-1/2 of your yearly salary buying a mustang?

Remember also we have emissions here in the US, and we have requirements to have recirculating unburned fuel those canisters, fuel filters, etc also are effected by the lower octane and deposit build-up.

Its real simple: 87 octane burns like oil, 93 octane burns like natural gas, which would you rather?

 

[Hack]

There's so much incorrect information in this thread I'm not even going to try to say something about all of it.

Lower octane fuel is not dirty or impure.
Lower octane fuel does not build up more unburned fuel. In fact, higher octane has more resistance to burning and so is MORE likely to not burn completely.

I agree with FordTechOne that the engine doesn't adjust to lower octane fuel after burning it, but I don't agree with any of his other statements. Ford recommends 87 octane fuel in the 5.0, so of course the engine was designed for 87 octane fuel!

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