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ajive

3.5L Ecoboost Octane vs Mileage

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ajive

So I noticed in the manual the subject engine calls for 87, but it recommends 91 for better performance while under heavy loads.  So with that, there are also some discussions on F150 forums about better gas mileage using 91.

Last weekend I did a test.  On a ~350 mile each way trip I ran 87 then 91.  The trip was mostly interstate with about an hour of smaller highways on the way to the OR coast.

I ended up getting an average of 17.9 MPG there and 21.2 MPG on the way back.  That's a pretty significant difference and normally worth the cost premium at the pump.

Does this seem legit?  There are obviously a lot of variables, but for the most part the trips we're pretty comparable.... Warm sunny days without much traffic, same route, cruise control whenever practical.

I feel like I'm a premium convert for this truck, but I don't want to be a sucker based on bad data! I'd like to try this again, but I don't really take a lot of long trips and that 36 gallon gas tank takes forever to wear down!

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Hemmy

I recently did this with my 2016 Yukon Denali 6.2.

Results from premium

85812AE3-3CA0-498F-8C05-8355E5FDEE20.thumb.jpeg.4c2e2b9856e0143179afc9fb3b551620.jpeg

87 results

C9146997-5824-4625-A9B8-6FF1E9B2DDB3.thumb.jpeg.8958242cbe356378b91a3810690d7304.jpeg

I am almost done with a third comparison with 87 and it is more in line with the first results from the premium.  These were all normal driving. Back and forth to work. Nothing out of the ordinary.

 

B8F33D95-6721-4353-B100-2028771D8A91.jpeg

Edited by Hemmy

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MLA

Were both grades E-10? was the load the same boat ways? 87 and 91 have roughly the BTU, so on paper, there would not be any performance difference in power. However, if the 87 had some spark knock, resulting in retarded timing, them the lower volatility 91 would allow the fuel and timing maps to run unmolested. This could explain the better MPG . 

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minnmarker

Wind? Up or down?

I can easily get 2 or 3 mpg difference with slight incline.

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Sixball

Yeper..  Many possibility's  that can do that to you. Wind, grade, even something as little as small throttle movement.  I have never seen that kind of change but I have not run 91 oct  but maybe three times.  But I have not seen it in my brothers Eco vehicles ether.  We did run a long pull last year running no E-10 and non E 91  oct.  Didn't see much and not enough to cover the cost.

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Hemmy
23 minutes ago, MLA said:

Were both grades E-10? was the load the same boat ways? 87 and 91 have roughly the BTU, so on paper, there would not be any performance difference in power. However, if the 87 had some spark knock, resulting in retarded timing, them the lower volatility 91 would allow the fuel and timing maps to run unmolested. This could explain the better MPG . 

Both were from Coatco so no more than E-10. The load of both trips were the same. I was not towing or loaded with anything. Trip itself was not identical, but similar. I only have 2 complete trips so I will keep an eye on a couple more trips with each grade of fuel and look for consistency.  I didn’t notice any knock either but I also recently put some 44K fuel injector cleaner in, however that wouldn’t make a difference between low and high octane.

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shawndoggy

FWIW I've towed with 91 and towed with 87.  No meaningful difference.  basically 9-10 mpg depending how deep my foot is in the throttle.  I want to convince myself that 91 is going to perform substantially better, but it doesn't (for me anyhow).

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ajive

There was a fair cross wind the way down so that could have played some.  The terrain is not much different from end to end, no mountain passes or anything... Net elevation gain of round trip was precisely 0' 😁.  The load was close, just a a weekend worth of food less.  All E10.

I don't know the nuts and bolts exactly, but I thought higher octane allowed for more compression and thus more power.  I know older engines were fixed based on a selected fuel, but I don't think that's the case anymore.  It wouldn't surprise me if the engines of today can make some adjustments to get the most out of the type of fuel in use.

It's probably a fluke, but I'll definitely try it again next time I have a long trip!

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Hemmy
8 minutes ago, shawndoggy said:

FWIW I've towed with 91 and towed with 87.  No meaningful difference.  basically 9-10 mpg depending how deep my foot is in the throttle.  I want to convince myself that 91 is going to perform substantially better, but it doesn't (for me anyhow).

I have seen guys on here saying they noticed a difference between the two and that is why I started comparing. I don’t think it would be a substantial difference on mpg.  The difference might be in the longevity of the engine. I mostly use 87 but every now and then I will throw in 91 to make me feel better about my car.  I also like to use fuel injector cleaner to help.

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MLA
24 minutes ago, Hemmy said:

I didn’t notice any knock

You may not hear it, but the engine sensors can, and retard the timing. 

9 minutes ago, Hemmy said:

 The difference might be in the longevity of the engine. I mostly use 87 but every now and then I will throw in 91 to make me feel better about my car

There is no real quality difference, in the two grades, just a difference in resistance to ignition. 

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Eagleboy99

The only benefit is to refinery company shareholders.  

From 2010 to 2014, a gallon of premium gasoline cost 7% to 10% more than regular, on average. In 2015, however, the price difference leapt to 17%, and in February 2016 it was up to 27%. In terms of real prices, in 2010 and 2011, the average gallon of premium cost around 25¢ more than regular. By 2015, the difference was 40¢, and last month it hit 48¢.

 

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edwin
1 hour ago, ajive said:

There was a fair cross wind the way down so that could have played some.  The terrain is not much different from end to end, no mountain passes or anything...

While not a direct comparison but the lack of aerodynamics is pretty similar, my Tundra trucks have never met a wind they like except for a tail wind.  Solid cross winds affect it a bit, but any wind on the front of the truck just kills the mileage.  

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granddaddy55

I think locking out six especially in uphill even slight long uphill , you don't get the motor in full twin turbo, when you don’t kick out six and the motor chugs up the hill in 6 you can feel the whole dash and even steering wheel vibrating from full twin , you feel that much less if at all when it down shifted.  

Someone in the last eco mileage forum recommended thst I do on my long 800 mile one way  lake trip snd I didn’t snd I could feel those twins vibrate the dash  about 1/2 the way up the long slight uphill climbs 

when I did  that at 74-79 mph I got 9.3 and all of my measurements were actual gallons divided by miles per stop for gas , more downhill I got 11+ , but flats snd uohill between 70-78 I got less than 10 using cruise cause I got tired of footing it and accelerating before going up, let the truck do it’s own  thing and shift wherever it wanted except if we got slowed down I didn’t just hit resume, I worked it back up and then resumed   

I have the 2.7, it might be less efficient at higher consistent highway speeds than the 3.5 but probably better in daily driving and local shorter slower tows based on a lot of op’s with 3.5’s seem to report better hwy   Mileage than I get but I wonder if their using the lie o meter

Edited by granddaddy55

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Cole2001

Not an f150 but my Mini Cooper gets at least 100-150 extra km when running the recommended 91 octane. Worth the money too me. 

This might also be a regional thing but I’ve found premium gas prices really vary. Shell is always 1.54, Esso is 1.48 and Costco is ussally 144.

My 440 raptor also seems to run a lot smoother on 91 than 89. 

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Bozboat

I drove my my 2012 F150 Ecoboost 96,000   Miles. Frequently I would see 3-4 mpg better mileage going with the wind vs against it. Even a 4-5 mph breeze would wreck the mpg at interstate speeds.  The average always stayed the same. 15-16 without the boat and just under 10 with it. It had the 3.73 rear end IIRC.

Edited by Bozboat

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carguy79ta

Off topic but I am sure that you have noticed it is tougher to surf into the wind also. 

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wakesonthesnake
On 9/28/2018 at 4:54 PM, ajive said:

 

Last weekend I did a test.  On a ~350 mile each way trip I ran 87 then 91.  The trip was mostly interstate with about an hour of smaller highways on the way to the OR coast.

I ended up getting an average of 17.9 MPG there and 21.2 MPG on the way back.  That's a pretty significant difference and normally worth the cost premium at the pump.

 

Every time I drive down the Columbia Gorge I get a couple of MPG better coming back.  Not saying octane doesn't make a difference but that is not the drive to prove it.  There is a reason it is one of the best wind surfing locations around.

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dlb

I thought octane was a knock issue solution these days.  There appears to be plenty of articles on the car sites that say if your vehicle is rated for 87 you are wasting your money on higher ratings.

In unleaded days octane may have been a mileage booster, but not today.

In our cars and SUV we fill with what is recommended and nothing more.  Too many gas tanks to fill, need to smart about it.

Edited by dlb

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oldjeep
On 9/28/2018 at 8:45 PM, MLA said:

There is no real quality difference, in the two grades, just a difference in resistance to ignition. 

Depends on where you buy your fuel.  Some brands like Holiday run a better additive package in the higher octane fuels. 

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MLA
16 minutes ago, oldjeep said:

Depends on where you buy your fuel.  Some brands like Holiday run a better additive package in the higher octane fuels. 

Could be a good debate if you are comparing 87 from one brand and high oct from another. However, comparing within the same brand, it will depend on your opinion of if those additive packages actually make the fuel better, then what it was coming out of the pipeline with the EPA mandated additive packages. My opinion, those proprietary additives serve 2 goals for the "brand". 1) sets them apart advertising wise, from the others. 2) allows them to justify the higher price of the higher octane. 

Could those extra additives add some benefits? Maybe. Are they worth the extra cost of running the higher then needed oct over the life of the vehicle, just for the extra additives? My opinion, no.

My main point was. There is a misconception based on marketing, that 87 octane is crap gasoline and will cause you engine problems, if you run it. This could not be further from the truth. If your engine compression and induction system dictate 87 is the proper fuel, then you can run it with no more chance of engine or fuel system issues, then any other higher grade.   

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Nitrousbird
On 9/28/2018 at 10:06 PM, Eagleboy99 said:

The only benefit is to refinery company shareholders.  

From 2010 to 2014, a gallon of premium gasoline cost 7% to 10% more than regular, on average. In 2015, however, the price difference leapt to 17%, and in February 2016 it was up to 27%. In terms of real prices, in 2010 and 2011, the average gallon of premium cost around 25¢ more than regular. By 2015, the difference was 40¢, and last month it hit 48¢.

 

I agree on the price insanity...but it doesn't just benefit shareholders.  Some motors need that additional octane....

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Eagleboy99
12 hours ago, Nitrousbird said:

I agree on the price insanity...but it doesn't just benefit shareholders.  Some motors need that additional octane....

Sure - "dumb" motors.  Otherwise the computer manages the detonation.  But keep buying overly expensive premium.  Great for my 401K!  :)

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Nitrousbird
46 minutes ago, Eagleboy99 said:

Sure - "dumb" motors.  Otherwise the computer manages the detonation.  But keep buying overly expensive premium.  Great for my 401K!  :)

You need to educate yourself before making such "dumb" blanket statements.  High boost / high compression motors, at least more modern stuff, have low-octane fueling tables typically.  They pull boost (if turbo) and/or timing to compensate.  Kills power right where you need it; WOT and low RPM/high TPMS = lower fuel mileage.  You'll end up spending more on fuel while your car performs poorly.  

Motor in my boat requires premium.  I wouldn't dare trust the Indmar mapping to have a reasonable low-octane table.  Same motor in all automotive applications also recommends premium and has been proven to see performance degradation running 87.  Motor in my BMW has to have premium - I can tell a difference in max boost just simply on running 92 vs 93 octane (mind you I'm running mapping targeting 2x stock boost with logic that will adjust for octane).  Wife's supercharged Audi also recommends premium.  I'm sure it will run well enough on 87, killing fuel economy in the process.

The REAL answer - you should run the lowest octane possible that will allow the motor to run without detection of knock.  For many motors, 87 is fine.  Some, 91+ is what is needed.  Others might call for 91 but get away with 89 without knock detection.  Ambient conditions and elevation can also impact the ultimate octane need.    

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Eagleboy99

Nice insult there pal. Real creative.  As you say "Motor in my boat requires premium" - why not run av gas in it then? I mean your thesis is that more (octane) is better right?

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JeffK

I think the answer is to run at the octane level suggested by the programmers, as they have likely (and hopefully) optimized the tables to match and that will be the point where you will get the best performance and efficiency blends across the board.  They want their motors to perform at their best, while minimizing wear and warranty issues/claims.  I'd say that alone would push me to follow their recommendations in octane levels.    I'm sure it will run at lower octane levels, but at what cost?

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