EcoBoosts, Fuel, Octane, Ethanol and Tuning...

[LokiWolf]

Do you have more power / accelerate faster with 91 octane vs 87 octane
AND ALSO (at the same time) get better gas mileage?

In other words does the rates of acceleration have to be the same
in order to get better MPG? Or is it one or the other but not both simultaneously?

Lets say, for the purposes of the question ... to achieve the max acceleration increase
or the max MPG increase

@JasonH is dead on above, but I get what you are saying.

With the same driving habits, MPG will increase with higher Octane. It you "use" the power more obviously the MPG will suffer. Your results per volume though are better. What I am saying is it takes less throttle to attain the same acceleration level with higher Octane. Hence why it improves MPG for most people.

 

[Uturn]

So far the discussion has been octane and mileage or power. My take on the benefits of higher octane is engine health. These engines can potentially suffer from low rpm knock. It gets more prevalent with low octane combined with a little oil vapor (hence the requirement for SN+ oil). The question to ask oneself is "is an extra 30 cents+ a gallon worth it a vehicle that costs in excess of $55k?". Frankly, I have my wife run midgrade just as a cheap insurance policy. It works out to $1200 (extended warranty cost?) in 80k miles.

 

[Saltwater Soul]

I have been keeping a mileage log for each tank that includes such things as:

• Price
• Octane (for the fillup and the "average" for the tank)
• Miles
• Hours
• Off road miles (usually loose sand which is really tough on the mpg)
• Tow miles (for each of 3 different sized trailers)
• Average Speed per tank

I don't have enough data points yet to make strong conclusions, but the simple regressions I have run so far indicate that each "point" of octane is worth about .15 mpg when I control for the other variables. I did this real quickly so I may change my conclusion with more data points or a better model.

Average speed for the tank ends up being a proxy for city/highway miles. Slower average speeds mean I was more stop and go. Faster average speed means I was on a freeway. MPG goes up with average speed (to a point).

 

[LokiWolf]

I have been keeping a mileage log for each tank that includes such things as:

• Price
• Octane (for the fillup and the "average" for the tank)
• Miles
• Hours
• Off road miles (usually loose sand which is really tough on the mpg)
• Tow miles (for each of 3 different sized trailers)
• Average Speed per tank

I don't have enough data points yet to make strong conclusions, but the simple regressions I have run so far indicate that each "point" of octane is worth about .15 mpg when I control for the other variables. I did this real quickly so I may change my conclusion with more data points or a better model.

Average speed for the tank ends up being a proxy for city/highway miles. Slower average speeds mean I was more stop and go. Faster average speed means I was on a freeway. MPG goes up with average speed (to a point).

Nice! Data is good!


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[LokiWolf]

So far the discussion has been octane and mileage or power. My take on the benefits of higher octane is engine health. These engines can potentially suffer from low rpm knock. It gets more prevalent with low octane combined with a little oil vapor (hence the requirement for SN+ oil). The question to ask oneself is "is an extra 30 cents+ a gallon worth it a vehicle that costs in excess of $55k?". Frankly, I have my wife run midgrade just as a cheap insurance policy. It works out to $1200 (extended warranty cost?) in 80k miles.

The EB pulls timing and fueling if it senses knocking, but yes, best way to prevent that from being an issue in the first place is to just run Higher Octane.


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[flying68]

I did my first 6000 or so miles on 87 octane and the last 7000 or so on 91 (highest available) and have not seen any difference in daily mpg. My highway mpg varies too much with wind conditions to see any difference yet (first 6000 had a lot of highway trips).

Side note, without keeping a log book this would be impossible because the dang trip computer is off as much as 1.5 mpg and it isn't consistent.

 

[Fozzy]

The EB pulls timing and fueling if it senses knocking, but yes, best way to prevent that from being an issue in the first place is to just run Higher Octane.


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Is there anyway to tell when it’s pulling timing and fuel? That would be great info to track. I have never heard any of my EB’s knock, but that doesn’t mean it’s not de fueling or pulling trimming.


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[LokiWolf]

Is there anyway to tell when it’s pulling timing and fuel? That would be great info to track. I have never heard any of my EB’s knock, but that doesn’t mean it’s not de fueling or pulling trimming.


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Yes! Got any way of logging or tracking PIDs? Like a MX+?


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[Fozzy]

Yes! Got any way of logging or tracking PIDs? Like a MX+?


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I do have a MX+ but have only used it to turn off the honk when left running. Do I need a special app?


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[LokiWolf]

I do have a MX+ but have only used it to turn off the honk when left running. Do I need a special app?


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The OBDLink App. Should have been a code with your MX+ to get advanced PIDs. Then you are looking for Knock Retard. I can find the specific name tomorrow when the wife is home with the Expy.


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